diff --git a/applications/utilities/finiteArea/makeFaMesh/findMeshDefinitionDict.H b/applications/utilities/finiteArea/makeFaMesh/findMeshDefinitionDict.H
index 956b3e3bf7..e1638a77ee 100644
--- a/applications/utilities/finiteArea/makeFaMesh/findMeshDefinitionDict.H
+++ b/applications/utilities/finiteArea/makeFaMesh/findMeshDefinitionDict.H
@@ -13,6 +13,19 @@ License
 Description
     Search for the appropriate faMeshDefinition dictionary...
 
+Required Classes
+    - Foam::polyMesh
+    - Foam::IOdictionary
+
+Required Variables
+    - regionName [word]
+    - args [argList]
+    - runTime [Time]
+
+Provided Variables
+    - meshDefDict [IOdictionary]
+    - meshDictPtr [autoPtr<IOdictionary>]
+
 \*---------------------------------------------------------------------------*/
 
 const word dictName("faMeshDefinition");
@@ -21,7 +34,7 @@ autoPtr<IOdictionary> meshDictPtr;
 
 {
     fileName dictPath;
-    const word& regionDir = polyMesh::regionName(regionName);
+    const word& regionDir = Foam::polyMesh::regionName(regionName);
 
     if (args.readIfPresent("dict", dictPath))
     {
diff --git a/applications/utilities/mesh/conversion/gmshToFoam/gmshToFoam.C b/applications/utilities/mesh/conversion/gmshToFoam/gmshToFoam.C
index 4e6a5b3a7c..77331991ab 100644
--- a/applications/utilities/mesh/conversion/gmshToFoam/gmshToFoam.C
+++ b/applications/utilities/mesh/conversion/gmshToFoam/gmshToFoam.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2020-2021 OpenCFD Ltd.
+    Copyright (C) 2020-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -1317,11 +1317,12 @@ int main(int argc, char *argv[])
     #include "setRootCase.H"
     #include "createTime.H"
 
-    word regionName(polyMesh::defaultRegion);
+    // Specified region or default region
+    #include "getRegionOption.H"
 
-    if (args.readIfPresent("region", regionName))
+    if (!polyMesh::regionName(regionName).empty())
     {
-        Info<< "Creating polyMesh for region " << regionName << endl;
+        Info<< "Creating polyMesh for region " << regionName << nl;
     }
 
     const bool keepOrientation = args.found("keepOrientation");
diff --git a/applications/utilities/mesh/generation/PDRblockMesh/cleanMeshDirectory.H b/applications/utilities/mesh/generation/PDRblockMesh/cleanMeshDirectory.H
index 9b0d60bebd..c1ef7dc62c 100644
--- a/applications/utilities/mesh/generation/PDRblockMesh/cleanMeshDirectory.H
+++ b/applications/utilities/mesh/generation/PDRblockMesh/cleanMeshDirectory.H
@@ -18,11 +18,10 @@ Description
 {
     // Shadows enclosing parameter (dictName)
     const word blockMeshDictName("blockMeshDict");
-    const word& regionDir = polyMesh::regionName(regionName);
 
     const fileName polyMeshPath
     (
-        runTime.path()/meshInstance/regionDir/polyMesh::meshSubDir
+        runTime.path()/meshInstance/polyMesh::meshDir(regionName)
     );
 
     if (exists(polyMeshPath))
diff --git a/applications/utilities/mesh/generation/blockMesh/blockMesh.C b/applications/utilities/mesh/generation/blockMesh/blockMesh.C
index a033155052..a09d631fd5 100644
--- a/applications/utilities/mesh/generation/blockMesh/blockMesh.C
+++ b/applications/utilities/mesh/generation/blockMesh/blockMesh.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2016-2022 OpenCFD Ltd.
+    Copyright (C) 2016-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -183,12 +183,12 @@ int main(int argc, char *argv[])
       : blockMesh::DEFAULT_MERGE
     );
 
-    word regionName(polyMesh::defaultRegion);
+    // Specified region or default region
+    #include "getRegionOption.H"
 
-    // Check if the region is specified otherwise mesh the default region
-    if (args.readIfPresent("region", regionName))
+    if (!polyMesh::regionName(regionName).empty())
     {
-        Info<< nl << "Generating mesh for region " << regionName << endl;
+        Info<< nl << "Generating mesh for region " << regionName << nl;
     }
 
     // Instance for resulting mesh
diff --git a/applications/utilities/mesh/generation/blockMesh/cleanMeshDirectory.H b/applications/utilities/mesh/generation/blockMesh/cleanMeshDirectory.H
index 9b0d60bebd..c1ef7dc62c 100644
--- a/applications/utilities/mesh/generation/blockMesh/cleanMeshDirectory.H
+++ b/applications/utilities/mesh/generation/blockMesh/cleanMeshDirectory.H
@@ -18,11 +18,10 @@ Description
 {
     // Shadows enclosing parameter (dictName)
     const word blockMeshDictName("blockMeshDict");
-    const word& regionDir = polyMesh::regionName(regionName);
 
     const fileName polyMeshPath
     (
-        runTime.path()/meshInstance/regionDir/polyMesh::meshSubDir
+        runTime.path()/meshInstance/polyMesh::meshDir(regionName)
     );
 
     if (exists(polyMeshPath))
diff --git a/applications/utilities/mesh/generation/blockMesh/findBlockMeshDict.H b/applications/utilities/mesh/generation/blockMesh/findBlockMeshDict.H
index 5dab776091..5c820b6aa6 100644
--- a/applications/utilities/mesh/generation/blockMesh/findBlockMeshDict.H
+++ b/applications/utilities/mesh/generation/blockMesh/findBlockMeshDict.H
@@ -38,7 +38,7 @@ autoPtr<IOdictionary> meshDictPtr;
         exists
         (
             runTime.path()/runTime.constant()
-          / regionDir/polyMesh::meshSubDir/dictName
+          / polyMesh::meshDir(regionName)/dictName
         )
     )
     {
@@ -47,7 +47,7 @@ autoPtr<IOdictionary> meshDictPtr;
         dictPath =
         (
             runTime.constant()
-          / regionDir/polyMesh::meshSubDir/dictName
+          / polyMesh::meshDir(regionName)/dictName
         );
 
 
diff --git a/applications/utilities/mesh/generation/extrude/extrudeMesh/extrudeMesh.C b/applications/utilities/mesh/generation/extrude/extrudeMesh/extrudeMesh.C
index 06823eb738..aed6edfbea 100644
--- a/applications/utilities/mesh/generation/extrude/extrudeMesh/extrudeMesh.C
+++ b/applications/utilities/mesh/generation/extrude/extrudeMesh/extrudeMesh.C
@@ -255,19 +255,17 @@ int main(int argc, char *argv[])
     #include "setRootCase.H"
     #include "createTimeExtruded.H"
 
-    // Get optional regionName
-    word regionName(polyMesh::defaultRegion);
-    if (args.readIfPresent("region", regionName))
-    {
-        Info<< "Create mesh " << regionName << " for time = "
-            << runTimeExtruded.timeName() << nl << endl;
-    }
-    else
-    {
-        Info<< "Create mesh for time = "
-            << runTimeExtruded.timeName() << nl << endl;
-    }
+    // Specified region or default region
+    #include "getRegionOption.H"
 
+    {
+        Info<< "Create mesh";
+        if (!polyMesh::regionName(regionName).empty())
+        {
+            Info<< ' ' << regionName;
+        }
+        Info<< " for time = " << runTimeExtruded.timeName() << nl << nl;
+    }
 
     const IOdictionary dict
     (
diff --git a/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C b/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C
index ab9b2657aa..decbb1aa56 100644
--- a/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C
+++ b/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C
@@ -1210,7 +1210,7 @@ void extrudeGeometricProperties
         (
             "patchFaceCentres",
             mesh.pointsInstance(),
-            mesh.meshSubDir,
+            polyMesh::meshSubDir,
             mesh,
             IOobject::MUST_READ
         )
@@ -1222,7 +1222,7 @@ void extrudeGeometricProperties
         (
             "patchEdgeCentres",
             mesh.pointsInstance(),
-            mesh.meshSubDir,
+            polyMesh::meshSubDir,
             mesh,
             IOobject::MUST_READ
         )
@@ -1268,7 +1268,7 @@ void extrudeGeometricProperties
         (
             "faceCentres",
             regionMesh.pointsInstance(),
-            regionMesh.meshSubDir,
+            polyMesh::meshSubDir,
             regionMesh,
             IOobject::NO_READ,
             IOobject::NO_WRITE,
@@ -1352,7 +1352,7 @@ void extrudeGeometricProperties
         (
             "cellCentres",
             regionMesh.pointsInstance(),
-            regionMesh.meshSubDir,
+            polyMesh::meshSubDir,
             regionMesh,
             IOobject::NO_READ,
             IOobject::NO_WRITE,
@@ -2555,7 +2555,7 @@ int main(int argc, char *argv[])
         (
             "cellToPatchFaceAddressing",
             regionMesh.facesInstance(),
-            regionMesh.meshSubDir,
+            polyMesh::meshSubDir,
             regionMesh,
             IOobject::NO_READ,
             IOobject::NO_WRITE,
@@ -2571,7 +2571,7 @@ int main(int argc, char *argv[])
         (
             "faceToPatchFaceAddressing",
             regionMesh.facesInstance(),
-            regionMesh.meshSubDir,
+            polyMesh::meshSubDir,
             regionMesh,
             IOobject::NO_READ,
             IOobject::NO_WRITE,
@@ -2588,7 +2588,7 @@ int main(int argc, char *argv[])
         (
             "faceToPatchEdgeAddressing",
             regionMesh.facesInstance(),
-            regionMesh.meshSubDir,
+            polyMesh::meshSubDir,
             regionMesh,
             IOobject::NO_READ,
             IOobject::NO_WRITE,
@@ -2605,7 +2605,7 @@ int main(int argc, char *argv[])
         (
             "pointToPatchPointAddressing",
             regionMesh.facesInstance(),
-            regionMesh.meshSubDir,
+            polyMesh::meshSubDir,
             regionMesh,
             IOobject::NO_READ,
             IOobject::NO_WRITE,
@@ -2647,7 +2647,7 @@ int main(int argc, char *argv[])
         (
             "patchFaceCentres",
             mesh.pointsInstance(),
-            mesh.meshSubDir,
+            polyMesh::meshSubDir,
             mesh,
             IOobject::MUST_READ
         );
diff --git a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshIO.C b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshIO.C
index d312a57f43..7f4ddccb0f 100644
--- a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshIO.C
+++ b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshIO.C
@@ -296,7 +296,7 @@ void Foam::conformalVoronoiMesh::writeMesh(const fileName& instance)
 //            (
 //                "pointDualAddressing",
 //                instance,
-//                "tetDualMesh"/polyMesh::meshSubDir,
+//                polyMesh::meshDir("tetDualMesh"),
 //                runTime_,
 //                IOobject::NO_READ,
 //                IOobject::NO_WRITE,
@@ -343,7 +343,7 @@ void Foam::conformalVoronoiMesh::writeMesh(const fileName& instance)
 //                (
 //                    "dualPoints",
 //                    instance,
-//                    "tetDualMesh"/polyMesh::meshSubDir,
+//                    polyMesh::meshDir("tetDualMesh"),
 //                    runTime_,
 //                    IOobject::NO_READ,
 //                    IOobject::NO_WRITE,
diff --git a/applications/utilities/mesh/manipulation/rotateMesh/rotateMesh.C b/applications/utilities/mesh/manipulation/rotateMesh/rotateMesh.C
index c798553561..2106a2b1cf 100644
--- a/applications/utilities/mesh/manipulation/rotateMesh/rotateMesh.C
+++ b/applications/utilities/mesh/manipulation/rotateMesh/rotateMesh.C
@@ -129,7 +129,7 @@ int main(int argc, char *argv[])
         const word& regionName = regionNames[regioni];
         const fileName meshDir
         (
-            polyMesh::regionName(regionName)/polyMesh::meshSubDir
+            polyMesh::meshDir(regionName)
         );
 
         if (regionNames.size() > 1)
diff --git a/applications/utilities/mesh/manipulation/setsToZones/setsToZones.C b/applications/utilities/mesh/manipulation/setsToZones/setsToZones.C
index a42a9ec7ee..f15e24dc09 100644
--- a/applications/utilities/mesh/manipulation/setsToZones/setsToZones.C
+++ b/applications/utilities/mesh/manipulation/setsToZones/setsToZones.C
@@ -86,7 +86,7 @@ int main(int argc, char *argv[])
 
     #include "createNamedPolyMesh.H"
 
-    const fileName setsSubPath(mesh.dbDir()/polyMesh::meshSubDir/"sets");
+    const fileName setsSubPath(mesh.meshDir()/"sets");
 
     // Search for list of objects for the time of the mesh
     word setsInstance = runTime.findInstance
diff --git a/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C b/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C
index fcb6469181..4594157462 100644
--- a/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C
+++ b/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C
@@ -894,7 +894,7 @@ void createAndWriteRegion
         (
             "pointRegionAddressing",
             newMesh().facesInstance(),
-            newMesh().meshSubDir,
+            polyMesh::meshSubDir,
             newMesh(),
             IOobject::NO_READ,
             IOobject::NO_WRITE,
@@ -913,7 +913,7 @@ void createAndWriteRegion
         (
             "faceRegionAddressing",
             newMesh().facesInstance(),
-            newMesh().meshSubDir,
+            polyMesh::meshSubDir,
             newMesh(),
             IOobject::NO_READ,
             IOobject::NO_WRITE,
@@ -951,7 +951,7 @@ void createAndWriteRegion
         (
             "cellRegionAddressing",
             newMesh().facesInstance(),
-            newMesh().meshSubDir,
+            polyMesh::meshSubDir,
             newMesh(),
             IOobject::NO_READ,
             IOobject::NO_WRITE,
@@ -970,7 +970,7 @@ void createAndWriteRegion
         (
             "boundaryRegionAddressing",
             newMesh().facesInstance(),
-            newMesh().meshSubDir,
+            polyMesh::meshSubDir,
             newMesh(),
             IOobject::NO_READ,
             IOobject::NO_WRITE,
diff --git a/applications/utilities/mesh/manipulation/transformPoints/createRegionMesh.H b/applications/utilities/mesh/manipulation/transformPoints/createRegionMesh.H
index 03066d6288..38b968ad96 100644
--- a/applications/utilities/mesh/manipulation/transformPoints/createRegionMesh.H
+++ b/applications/utilities/mesh/manipulation/transformPoints/createRegionMesh.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2021 OpenCFD Ltd.
+    Copyright (C) 2021-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -22,12 +22,14 @@ Provided Variables
 
 \*---------------------------------------------------------------------------*/
 
-Foam::Info << "Create mesh";
-if (regionName != Foam::polyMesh::defaultRegion)
 {
-    Foam::Info << ' ' << regionName;
+    Foam::Info << "Create mesh";
+    if (!Foam::polyMesh::regionName(regionName).empty())
+    {
+        Foam::Info << ' ' << regionName;
+    }
+    Foam::Info << " for time = " << runTime.timeName() << Foam::nl;
 }
-Foam::Info << " for time = " << runTime.timeName() << Foam::nl;
 
 Foam::fvMesh mesh
 (
diff --git a/applications/utilities/mesh/manipulation/transformPoints/transformPoints.C b/applications/utilities/mesh/manipulation/transformPoints/transformPoints.C
index 05335a7f32..c339fde851 100644
--- a/applications/utilities/mesh/manipulation/transformPoints/transformPoints.C
+++ b/applications/utilities/mesh/manipulation/transformPoints/transformPoints.C
@@ -396,7 +396,7 @@ int main(int argc, char *argv[])
         const word& regionName = regionNames[regioni];
         const fileName meshDir
         (
-            polyMesh::regionName(regionName)/polyMesh::meshSubDir
+            polyMesh::meshDir(regionName)
         );
 
         if (regionNames.size() > 1)
diff --git a/applications/utilities/miscellaneous/foamFormatConvert/foamFormatConvert.C b/applications/utilities/miscellaneous/foamFormatConvert/foamFormatConvert.C
index 760474570f..a75f0ed650 100644
--- a/applications/utilities/miscellaneous/foamFormatConvert/foamFormatConvert.C
+++ b/applications/utilities/miscellaneous/foamFormatConvert/foamFormatConvert.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2016-2022 OpenCFD Ltd.
+    Copyright (C) 2016-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -296,15 +296,16 @@ int main(int argc, char *argv[])
     IOobject::fileModificationChecking = IOobject::timeStamp;
 
 
-    word regionName(polyMesh::defaultRegion);
-    if (args.readIfPresent("region", regionName))
+    // Specified region or default region
+    #include "getRegionOption.H"
+    if (!polyMesh::regionName(regionName).empty())
     {
         Info<< "Using region " << regionName << nl << endl;
     }
 
     const fileName meshDir
     (
-        polyMesh::regionName(regionName)/polyMesh::meshSubDir
+        polyMesh::meshDir(regionName)
     );
 
 
diff --git a/applications/utilities/parallelProcessing/decomposePar/decomposePar.C b/applications/utilities/parallelProcessing/decomposePar/decomposePar.C
index 130bf98a46..7676ec50d1 100644
--- a/applications/utilities/parallelProcessing/decomposePar/decomposePar.C
+++ b/applications/utilities/parallelProcessing/decomposePar/decomposePar.C
@@ -813,11 +813,7 @@ int main(int argc, char *argv[])
                     IOobject io
                     (
                         "faBoundary",
-                        mesh.time().findInstance
-                        (
-                            mesh.dbDir()/polyMesh::meshSubDir,
-                            "boundary"
-                        ),
+                        mesh.time().findInstance(mesh.meshDir(), "boundary"),
                         faMesh::meshSubDir,
                         mesh,
                         IOobject::READ_IF_PRESENT,
diff --git a/applications/utilities/parallelProcessing/reconstructParMesh/reconstructParMesh.C b/applications/utilities/parallelProcessing/reconstructParMesh/reconstructParMesh.C
index feb14f0c40..eb844f5779 100644
--- a/applications/utilities/parallelProcessing/reconstructParMesh/reconstructParMesh.C
+++ b/applications/utilities/parallelProcessing/reconstructParMesh/reconstructParMesh.C
@@ -305,7 +305,7 @@ autoPtr<mapPolyMesh> mergeSharedPoints
 boundBox procBounds
 (
     const PtrList<Time>& databases,
-    const word& regionDir
+    const word& regionName
 )
 {
     boundBox bb;
@@ -316,7 +316,7 @@ boundBox procBounds
         (
             procDb.findInstance
             (
-                regionDir/polyMesh::meshSubDir,
+                polyMesh::meshDir(regionName),
                 "points"
             )
         );
@@ -345,10 +345,10 @@ boundBox procBounds
                 "points",
                 procDb.findInstance
                 (
-                    regionDir/polyMesh::meshSubDir,
+                    polyMesh::meshDir(regionName),
                     "points"
                 ),
-                regionDir/polyMesh::meshSubDir,
+                polyMesh::meshDir(regionName),
                 procDb,
                 IOobject::MUST_READ,
                 IOobject::NO_WRITE,
@@ -771,7 +771,7 @@ int main(int argc, char *argv[])
             (
                 "faces",
                 databases[0].timeName(),
-                polyMesh::regionName(regionName)/polyMesh::meshSubDir,
+                polyMesh::meshDir(regionName),
                 databases[0],
                 IOobject::NO_READ,
                 IOobject::NO_WRITE
diff --git a/applications/utilities/parallelProcessing/redistributePar/loadOrCreateMesh.C b/applications/utilities/parallelProcessing/redistributePar/loadOrCreateMesh.C
index aae5cedb13..4b173340d3 100644
--- a/applications/utilities/parallelProcessing/redistributePar/loadOrCreateMesh.C
+++ b/applications/utilities/parallelProcessing/redistributePar/loadOrCreateMesh.C
@@ -275,7 +275,7 @@ void Foam::masterMeshInstance
 {
     const fileName meshSubDir
     (
-        polyMesh::regionName(io.name()) / polyMesh::meshSubDir
+        polyMesh::meshDir(io.name())
     );
 
     if (UPstream::master())
diff --git a/applications/utilities/parallelProcessing/redistributePar/redistributePar.C b/applications/utilities/parallelProcessing/redistributePar/redistributePar.C
index caef6f9611..8324c2134e 100644
--- a/applications/utilities/parallelProcessing/redistributePar/redistributePar.C
+++ b/applications/utilities/parallelProcessing/redistributePar/redistributePar.C
@@ -1577,14 +1577,20 @@ int main(int argc, char *argv[])
         forAll(regionNames, regioni)
         {
             const word& regionName = regionNames[regioni];
-            const word& regionDir = polyMesh::regionName(regionName);
 
-            const fileName volMeshSubDir(regionDir/polyMesh::meshSubDir);
-            const fileName areaMeshSubDir(regionDir/faMesh::meshSubDir);
+            const fileName volMeshSubDir
+            (
+                polyMesh::meshDir(regionName)
+            );
+            const fileName areaMeshSubDir
+            (
+                polyMesh::regionName(regionName) / faMesh::meshSubDir
+            );
 
             InfoOrPout
                 << nl
-                << "Reconstructing mesh " << regionDir << nl << endl;
+                << "Reconstructing mesh:"
+                << polyMesh::regionName(regionName) << nl << endl;
 
             bool areaMeshDetected = false;
 
@@ -2474,15 +2480,20 @@ int main(int argc, char *argv[])
         forAll(regionNames, regioni)
         {
             const word& regionName = regionNames[regioni];
-            const word& regionDir = polyMesh::regionName(regionName);
 
-            const fileName volMeshSubDir(regionDir/polyMesh::meshSubDir);
-            const fileName areaMeshSubDir(regionDir/faMesh::meshSubDir);
+            const fileName volMeshSubDir
+            (
+                polyMesh::meshDir(regionName)
+            );
+            const fileName areaMeshSubDir
+            (
+                polyMesh::regionName(regionName) / faMesh::meshSubDir
+            );
 
             InfoOrPout
                 << nl << nl
                 << (decompose ? "Decomposing" : "Redistributing")
-                << " mesh " << regionDir << nl << endl;
+                << " mesh:" << polyMesh::regionName(regionName) << nl << endl;
 
 
             // Get time instance directory
diff --git a/applications/utilities/postProcessing/dataConversion/foamToTetDualMesh/foamToTetDualMesh.C b/applications/utilities/postProcessing/dataConversion/foamToTetDualMesh/foamToTetDualMesh.C
index 09c72fd744..281f4d8aa1 100644
--- a/applications/utilities/postProcessing/dataConversion/foamToTetDualMesh/foamToTetDualMesh.C
+++ b/applications/utilities/postProcessing/dataConversion/foamToTetDualMesh/foamToTetDualMesh.C
@@ -184,7 +184,7 @@ int main(int argc, char *argv[])
         (
             "pointDualAddressing",
             tetDualMesh.facesInstance(),
-            tetDualMesh.meshSubDir,
+            polyMesh::meshSubDir,
             tetDualMesh,
             IOobject::MUST_READ
         )
diff --git a/applications/utilities/preProcessing/changeDictionary/changeDictionary.C b/applications/utilities/preProcessing/changeDictionary/changeDictionary.C
index bf9ba8911a..6d46b06097 100644
--- a/applications/utilities/preProcessing/changeDictionary/changeDictionary.C
+++ b/applications/utilities/preProcessing/changeDictionary/changeDictionary.C
@@ -540,7 +540,7 @@ int main(int argc, char *argv[])
                 "boundary",
                 runTime.findInstance
                 (
-                    polyMesh::regionName(regionName)/polyMesh::meshSubDir,
+                    polyMesh::meshDir(regionName),
                     "boundary",
                     IOobject::READ_IF_PRESENT
                 ),
diff --git a/applications/utilities/preProcessing/createZeroDirectory/boundaryInfo.C b/applications/utilities/preProcessing/createZeroDirectory/boundaryInfo.C
index 3be107a0da..f6dfb55633 100644
--- a/applications/utilities/preProcessing/createZeroDirectory/boundaryInfo.C
+++ b/applications/utilities/preProcessing/createZeroDirectory/boundaryInfo.C
@@ -54,8 +54,8 @@ Foam::IOPtrList<Foam::entry> Foam::boundaryInfo::readBoundaryDict
         IOobject
         (
             "boundary",
-            runTime.findInstance(regionName/polyMesh::meshSubDir, "boundary"),
-            regionName/polyMesh::meshSubDir,
+            runTime.findInstance(polyMesh::meshDir(regionName), "boundary"),
+            polyMesh::meshDir(regionName),
             runTime,
             IOobject::MUST_READ,
             IOobject::NO_WRITE,
diff --git a/applications/utilities/preProcessing/foamUpgradeCyclics/foamUpgradeCyclics.C b/applications/utilities/preProcessing/foamUpgradeCyclics/foamUpgradeCyclics.C
index 37ea689149..1855251592 100644
--- a/applications/utilities/preProcessing/foamUpgradeCyclics/foamUpgradeCyclics.C
+++ b/applications/utilities/preProcessing/foamUpgradeCyclics/foamUpgradeCyclics.C
@@ -409,15 +409,13 @@ int main(int argc, char *argv[])
     }
     const bool enableEntries = args.found("enableFunctionEntries");
 
-    const word regionName =
-        args.getOrDefault<word>("region", polyMesh::defaultRegion);
-
     fileName regionPrefix;
-    if (regionName != polyMesh::defaultRegion)
     {
-        regionPrefix = regionName;
-    }
+        // Specified region or default region
+        #include "getRegionOption.H"
 
+        regionPrefix = polyMesh::regionName(regionName);
+    }
 
     // Per cyclic patch the new name for this side and the other side
     HashTable<word> thisNames;
diff --git a/src/OpenFOAM/include/addAllRegionOptions.H b/src/OpenFOAM/include/addAllRegionOptions.H
index 24c35c1cdb..b916574dfd 100644
--- a/src/OpenFOAM/include/addAllRegionOptions.H
+++ b/src/OpenFOAM/include/addAllRegionOptions.H
@@ -13,6 +13,9 @@ License
 Description
     Add multi-region command-line options: -allRegions, -regions, -region
 
+Required Classes
+    - Foam::argList
+
 See Also
     getAllRegionOptions.H
 
diff --git a/src/OpenFOAM/include/addRegionOption.H b/src/OpenFOAM/include/addRegionOption.H
index b1946812da..821a49127b 100644
--- a/src/OpenFOAM/include/addRegionOption.H
+++ b/src/OpenFOAM/include/addRegionOption.H
@@ -1,6 +1,32 @@
-Foam::argList::addOption
-(
-    "region",
-    "name",
-    "Specify alternative mesh region"
-);
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2011 OpenFOAM Foundation
+    Copyright (C) 2023 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
+
+Description
+    Add -region option
+
+Required Classes
+    - Foam::argList
+
+\*---------------------------------------------------------------------------*/
+
+{
+    Foam::argList::addOption
+    (
+        "region",
+        "name",
+        "Specify mesh region (default: region0)"
+    );
+}
+
+
+// ************************************************************************* //
diff --git a/src/OpenFOAM/include/addTimeOptions.H b/src/OpenFOAM/include/addTimeOptions.H
index 42d4543d83..ca1694e47c 100644
--- a/src/OpenFOAM/include/addTimeOptions.H
+++ b/src/OpenFOAM/include/addTimeOptions.H
@@ -1,3 +1,24 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2011 OpenFOAM Foundation
+    Copyright (C) 2023 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
+
+Description
+    Add various time-related options (see Foam::timeSelector)
+
+Required Classes
+    - Foam::argList
+
+\*---------------------------------------------------------------------------*/
+
 Foam::argList::addBoolOption
 (
     "constant",
@@ -22,3 +43,5 @@ Foam::argList::addOption
     "time",
     "specify a single time value to select"
 );
+
+// ************************************************************************* //
diff --git a/src/OpenFOAM/include/createMesh.H b/src/OpenFOAM/include/createMesh.H
index 2e48efad50..b90149bd25 100644
--- a/src/OpenFOAM/include/createMesh.H
+++ b/src/OpenFOAM/include/createMesh.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018-2021 OpenCFD Ltd.
+    Copyright (C) 2018-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -14,6 +14,10 @@ Description
     Create a fvMesh (specified region or defaultRegion) with
     additional handling of -dry-run and -dry-run-write options.
 
+Required Classes
+    - Foam::fvMesh
+    - Foam::simplifiedMeshes::columnFvMesh
+
 Required Variables
     - args [argList]
     - runTime [Time]
@@ -26,7 +30,12 @@ Provided Variables
 \*---------------------------------------------------------------------------*/
 
 Foam::autoPtr<Foam::fvMesh> meshPtr(nullptr);
-Foam::word regionName(Foam::polyMesh::defaultRegion);
+
+// "getRegionOption.H"
+Foam::word regionName
+(
+    args.getOrDefault<word>("region", Foam::polyMesh::defaultRegion)
+);
 
 if (args.dryRun() || args.found("dry-run-write"))
 {
@@ -34,9 +43,6 @@ if (args.dryRun() || args.found("dry-run-write"))
         << "Operating in 'dry-run' mode: case will run for 1 time step.  "
         << "All checks assumed OK on a clean exit" << Foam::endl;
 
-    // Allow region in combination with dry-run
-    args.readIfPresent("region", regionName);
-
     Foam::FieldBase::allowConstructFromLargerSize = true;
 
     // Create a simplified 1D mesh and attempt to re-create boundary conditions
@@ -68,7 +74,7 @@ if (args.dryRun() || args.found("dry-run-write"))
 else
 {
     Foam::Info << "Create mesh";
-    if (args.readIfPresent("region", regionName))
+    if (!Foam::polyMesh::regionName(regionName).empty())
     {
         Foam::Info << ' ' << regionName;
     }
diff --git a/src/OpenFOAM/include/createNamedMesh.H b/src/OpenFOAM/include/createNamedMesh.H
index 05a9594ea6..b0785a10b1 100644
--- a/src/OpenFOAM/include/createNamedMesh.H
+++ b/src/OpenFOAM/include/createNamedMesh.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011 OpenFOAM Foundation
-    Copyright (C) 2021 OpenCFD Ltd.
+    Copyright (C) 2021-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -14,6 +14,9 @@ License
 Description
     Create a fvMesh for a specified region, or the defaultRegion
 
+Required Classes
+    - Foam::fvMesh
+
 Required Variables
     - args [argList]
     - runTime [Time]
@@ -24,11 +27,15 @@ Provided Variables
 
 \*---------------------------------------------------------------------------*/
 
-Foam::word regionName(Foam::polyMesh::defaultRegion);
+// "getRegionOption.H"
+Foam::word regionName
+(
+    args.getOrDefault<word>("region", Foam::polyMesh::defaultRegion)
+);
 
 {
     Foam::Info << "Create mesh";
-    if (args.readIfPresent("region", regionName))
+    if (!Foam::polyMesh::regionName(regionName).empty())
     {
         Foam::Info << ' ' << regionName;
     }
diff --git a/src/OpenFOAM/include/createNamedPolyMesh.H b/src/OpenFOAM/include/createNamedPolyMesh.H
index d1dbcaadbd..ef867de3f8 100644
--- a/src/OpenFOAM/include/createNamedPolyMesh.H
+++ b/src/OpenFOAM/include/createNamedPolyMesh.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011 OpenFOAM Foundation
-    Copyright (C) 2021 OpenCFD Ltd.
+    Copyright (C) 2021-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -14,7 +14,11 @@ License
 Description
     Create a polyMesh for a specified region, or the defaultRegion
 
+Required Classes
+    - Foam::polyMesh
+
 Required Variables
+    - args [argList]
     - runTime [Time]
 
 Provided Variables
@@ -23,11 +27,15 @@ Provided Variables
 
 \*---------------------------------------------------------------------------*/
 
-Foam::word regionName(Foam::polyMesh::defaultRegion);
+// "getRegionOption.H"
+Foam::word regionName
+(
+    args.getOrDefault<word>("region", Foam::polyMesh::defaultRegion)
+);
 
 {
     Foam::Info << "Create polyMesh";
-    if (args.readIfPresent("region", regionName))
+    if (!Foam::polyMesh::regionName(regionName).empty())
     {
         Foam::Info << ' ' << regionName;
     }
diff --git a/src/OpenFOAM/include/createNamedPolyMeshes.H b/src/OpenFOAM/include/createNamedPolyMeshes.H
index 116cda4b53..669dddbb54 100644
--- a/src/OpenFOAM/include/createNamedPolyMeshes.H
+++ b/src/OpenFOAM/include/createNamedPolyMeshes.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2022 OpenCFD Ltd.
+    Copyright (C) 2022-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -32,13 +32,13 @@ Foam::PtrList<Foam::polyMesh> meshes(regionNames.size());
 {
     forAll(regionNames, regioni)
     {
-        const Foam::word& regionName = regionNames[regioni];
+        const auto& regionName = regionNames[regioni];
 
         Foam::Info<< "Create polyMesh";
         if
         (
             regionNames.size() > 1
-         || regionName != Foam::polyMesh::defaultRegion
+         || !Foam::polyMesh::regionName(regionName).empty()
         )
         {
             Foam::Info<< ' ' << regionName;
diff --git a/src/OpenFOAM/include/getAllRegionOptions.H b/src/OpenFOAM/include/getAllRegionOptions.H
index 46476ec323..b77d0343aa 100644
--- a/src/OpenFOAM/include/getAllRegionOptions.H
+++ b/src/OpenFOAM/include/getAllRegionOptions.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2021 OpenCFD Ltd.
+    Copyright (C) 2021-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -23,6 +23,11 @@ Note
     There is no semantical difference between "-regions name"
     and "-region name"
 
+Required Classes
+    - Foam::polyMesh
+    - Foam::regionProperties
+    - Foam::IOobjectOption
+
 Required Variables
     - args [argList]
     - runTime [Time]
@@ -42,7 +47,10 @@ wordList regionNames;
     if (args.found("allRegions"))
     {
         regionNames =
-            regionProperties(runTime, IOobject::READ_IF_PRESENT).names();
+        (
+            Foam::regionProperties(runTime, IOobjectOption::READ_IF_PRESENT)
+            .names()
+        );
 
         if (regionNames.empty())
         {
@@ -60,17 +68,20 @@ wordList regionNames;
         if
         (
             selectByName.size() == 1
-         && selectByName.first().isLiteral()
+         && selectByName.front().isLiteral()
         )
         {
             // Identical to -region NAME
             regionNames.resize(1);
-            regionNames.first() = selectByName.first();
+            regionNames.front() = selectByName.front();
         }
         else if (selectByName.size())
         {
             regionNames =
-                regionProperties(runTime, IOobject::READ_IF_PRESENT).names();
+            (
+                Foam::regionProperties(runTime, IOobjectOption::READ_IF_PRESENT)
+                .names()
+            );
 
             if (regionNames.empty())
             {
@@ -99,14 +110,14 @@ wordList regionNames;
     else if (args.found("region"))
     {
         regionNames.resize(1);
-        regionNames.first() = args.get<word>("region");
+        regionNames.front() = args.get<word>("region");
     }
 
     // Fallback to defaultRegion
     if (regionNames.empty())
     {
         regionNames.resize(1);
-        regionNames.first() = polyMesh::defaultRegion;
+        regionNames.front() = Foam::polyMesh::defaultRegion;
     }
 }
 
diff --git a/src/OpenFOAM/include/getRegionOption.H b/src/OpenFOAM/include/getRegionOption.H
new file mode 100644
index 0000000000..a24df49e85
--- /dev/null
+++ b/src/OpenFOAM/include/getRegionOption.H
@@ -0,0 +1,33 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2023 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
+
+Description
+    Get the value from the -region option
+
+Required Classes
+    - Foam::polyMesh
+
+Required Variables
+    - args [argList]
+
+Provided Variables
+    - regionName [word]
+
+\*---------------------------------------------------------------------------*/
+
+Foam::word regionName
+(
+    args.getOrDefault<word>("region", Foam::polyMesh::defaultRegion)
+);
+
+
+// ************************************************************************* //
diff --git a/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalMeshData.C b/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalMeshData.C
index 7fd3cb883b..ea702a3edb 100644
--- a/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalMeshData.C
+++ b/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalMeshData.C
@@ -1829,7 +1829,7 @@ const Foam::labelList& Foam::globalMeshData::sharedPointGlobalLabels() const
         IOobject addrHeader
         (
             "pointProcAddressing",
-            mesh_.facesInstance()/mesh_.meshSubDir,
+            mesh_.facesInstance()/polyMesh::meshSubDir,
             mesh_,
             IOobject::MUST_READ
         );
diff --git a/src/OpenFOAM/meshes/polyMesh/polyMesh.C b/src/OpenFOAM/meshes/polyMesh/polyMesh.C
index 27077ae7a6..00480e7669 100644
--- a/src/OpenFOAM/meshes/polyMesh/polyMesh.C
+++ b/src/OpenFOAM/meshes/polyMesh/polyMesh.C
@@ -47,6 +47,7 @@ namespace Foam
 }
 
 Foam::word Foam::polyMesh::defaultRegion = "region0";
+
 Foam::word Foam::polyMesh::meshSubDir = "polyMesh";
 
 
@@ -820,11 +821,22 @@ const Foam::word& Foam::polyMesh::regionName(const word& region)
 }
 
 
+Foam::fileName Foam::polyMesh::meshDir(const word& region)
+{
+    if (region.empty() || region == polyMesh::defaultRegion)
+    {
+        return polyMesh::meshSubDir;
+    }
+
+    return (region / polyMesh::meshSubDir);
+}
+
+
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 const Foam::fileName& Foam::polyMesh::dbDir() const
 {
-    if (objectRegistry::dbDir() == defaultRegion)
+    if (objectRegistry::name() == polyMesh::defaultRegion)
     {
         return parent().dbDir();
     }
diff --git a/src/OpenFOAM/meshes/polyMesh/polyMesh.H b/src/OpenFOAM/meshes/polyMesh/polyMesh.H
index 8cf4f8efca..d4d6c0c15e 100644
--- a/src/OpenFOAM/meshes/polyMesh/polyMesh.H
+++ b/src/OpenFOAM/meshes/polyMesh/polyMesh.H
@@ -426,6 +426,10 @@ public:
 
         // Regions
 
+            //- Return the local mesh directory name (eg, "polyMesh")
+            //- after applying filter for defaultRegion
+            static fileName meshDir(const word& region);
+
             //- The mesh region name or word::null if polyMesh::defaultRegion
             static const word& regionName(const word& region);
 
diff --git a/src/dynamicFvMesh/include/createNamedDynamicFvMesh.H b/src/dynamicFvMesh/include/createNamedDynamicFvMesh.H
index dd659f2481..445e738131 100644
--- a/src/dynamicFvMesh/include/createNamedDynamicFvMesh.H
+++ b/src/dynamicFvMesh/include/createNamedDynamicFvMesh.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2012 OpenFOAM Foundation
-    Copyright (C) 2022 OpenCFD Ltd.
+    Copyright (C) 2022-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -14,40 +14,49 @@ License
 Description
     Create a dynamicFvMesh for a specified region, or the defaultRegion
 
+Required Classes
+    - Foam::dynamicFvMesh
+
 Required Variables
+    - args [argList]
     - runTime [Time]
 
 Provided Variables
     - regionName [word]
-    - mesh [dynamicFvMesh], meshPtr
+    - mesh [dynamicFvMesh]
+    - meshPtr [autoPtr<dynamicFvMesh>]
 
 \*---------------------------------------------------------------------------*/
 
-Foam::word regionName(Foam::polyMesh::defaultRegion);
 Foam::autoPtr<Foam::dynamicFvMesh> meshPtr;
 
+// "getRegionOption.H"
+Foam::word regionName
+(
+    args.getOrDefault<word>("region", Foam::polyMesh::defaultRegion)
+);
+
 {
     Foam::Info << "Create dynamic mesh";
-    if (args.readIfPresent("region", regionName))
+    if (!Foam::polyMesh::regionName(regionName).empty())
     {
         Foam::Info << ' ' << regionName;
     }
     Foam::Info << " for time = " << runTime.timeName() << Foam::nl;
 
-    meshPtr = dynamicFvMesh::New
+    meshPtr = Foam::dynamicFvMesh::New
     (
-        IOobject
+        Foam::IOobject
         (
             regionName,
             runTime.timeName(),
             runTime,
-            IOobject::MUST_READ
+            Foam::IOobject::MUST_READ
         )
     );
 }
 
-
-dynamicFvMesh& mesh = meshPtr();
+Foam::dynamicFvMesh& mesh = meshPtr();
 
 Foam::Info << Foam::endl;
 
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
index ce5548367c..373815305f 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
@@ -5671,7 +5671,7 @@ void Foam::hexRef8::removeFiles(const polyMesh& mesh)
     (
         "dummy",
         mesh.facesInstance(),
-        mesh.meshSubDir,
+        polyMesh::meshSubDir,
         mesh
     );
     fileName setsDir(io.path());
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/refinementHistory.C b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/refinementHistory.C
index bd85c5a369..3239bf801a 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/refinementHistory.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/refinementHistory.C
@@ -1699,7 +1699,7 @@ void Foam::refinementHistory::removeFiles(const polyMesh& mesh)
     (
         "dummy",
         mesh.facesInstance(),
-        mesh.meshSubDir,
+        polyMesh::meshSubDir,
         mesh
     );
     fileName setsDir(io.path());
diff --git a/src/finiteArea/faMesh/faMesh.H b/src/finiteArea/faMesh/faMesh.H
index ebe866b5c7..c644300081 100644
--- a/src/finiteArea/faMesh/faMesh.H
+++ b/src/finiteArea/faMesh/faMesh.H
@@ -722,6 +722,9 @@ public:
             return thisDb().name();
         }
 
+
+    // Regions
+
         //- The mesh region name or word::null if polyMesh::defaultRegion
         const word& regionName() const;
 
diff --git a/src/finiteArea/include/addFaRegionOption.H b/src/finiteArea/include/addFaRegionOption.H
new file mode 100644
index 0000000000..6b8ee6b7fc
--- /dev/null
+++ b/src/finiteArea/include/addFaRegionOption.H
@@ -0,0 +1,31 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2023 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
+
+Description
+    Add -area-region option
+
+Required Classes
+    - Foam::argList
+
+\*---------------------------------------------------------------------------*/
+
+{
+    Foam::argList::addOption
+    (
+        "area-region",
+        "name",
+        "Specify area-mesh region"
+   );
+}
+
+
+// ************************************************************************* //
diff --git a/src/finiteArea/include/createFaMesh.H b/src/finiteArea/include/createFaMesh.H
index 3f81084718..7fb6c25a05 100644
--- a/src/finiteArea/include/createFaMesh.H
+++ b/src/finiteArea/include/createFaMesh.H
@@ -1 +1,34 @@
-    faMesh aMesh(mesh);
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2016 Wikki Ltd
+    Copyright (C) 2023 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
+
+Description
+    Create a finite-area mesh for the defaultRegion
+
+Required Variables
+    - mesh [polyMesh]
+
+Provided Variables
+    - aMesh [faMesh]
+
+\*---------------------------------------------------------------------------*/
+
+Foam::Info << "Create finite-area mesh";
+Foam::Info << Foam::nl;
+
+Foam::faMesh aMesh
+(
+    mesh
+);
+
+
+// ************************************************************************* //
diff --git a/src/finiteArea/include/createNamedFaMesh.H b/src/finiteArea/include/createNamedFaMesh.H
new file mode 100644
index 0000000000..a1394aa7a9
--- /dev/null
+++ b/src/finiteArea/include/createNamedFaMesh.H
@@ -0,0 +1,53 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2023 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
+
+Description
+    Create a finite-area mesh for a specified region, or the defaultRegion
+
+Required Classes
+    - Foam::polyMesh
+
+Required Variables
+    - mesh [polyMesh]
+    - runTime [Time]
+
+Provided Variables
+    - areaRegionName [word]
+    - aMesh [faMesh]
+
+\*---------------------------------------------------------------------------*/
+
+// "getFaRegionOption.H"
+Foam::word areaRegionName
+(
+    args.getOrDefault<word>("area-region", Foam::polyMesh::defaultRegion)
+);
+
+{
+    Foam::Info << "Create finite-area mesh";
+    if (!Foam::polyMesh::regionName(areaRegionName).empty())
+    {
+        Foam::Info << ' ' << areaRegionName;
+    }
+    Foam::Info << " for time = " << runTime.timeName() << Foam::nl;
+}
+
+Foam::faMesh aMesh
+(
+    areaRegionName,
+    mesh
+);
+
+Foam::Info << Foam::endl;
+
+
+// ************************************************************************* //
diff --git a/src/finiteArea/include/getFaRegionOption.H b/src/finiteArea/include/getFaRegionOption.H
new file mode 100644
index 0000000000..3ce1682802
--- /dev/null
+++ b/src/finiteArea/include/getFaRegionOption.H
@@ -0,0 +1,33 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2023 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
+
+Description
+    Get the value from the -area-region option
+
+Required Classes
+    - Foam::polyMesh
+
+Required Variables
+    - args [argList]
+
+Provided Variables
+    - areaRegionName [word]
+
+\*---------------------------------------------------------------------------*/
+
+Foam::word areaRegionName
+(
+    args.getOrDefault<word>("area-region", Foam::polyMesh::defaultRegion)
+);
+
+
+// ************************************************************************* //
diff --git a/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.C b/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.C
index 9128a1b318..b647efca8c 100644
--- a/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.C
+++ b/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.C
@@ -461,7 +461,7 @@ Foam::fvMeshTools::newMesh
 
     const fileName meshSubDir
     (
-        polyMesh::regionName(io.name()) / polyMesh::meshSubDir
+        polyMesh::meshDir(io.name())
     );
 
 
@@ -745,7 +745,7 @@ Foam::fvMeshTools::loadOrCreateMeshImpl
 
     const fileName meshSubDir
     (
-        polyMesh::regionName(io.name()) / polyMesh::meshSubDir
+        polyMesh::meshDir(io.name())
     );
 
 
diff --git a/src/finiteVolume/fvMesh/simplifiedFvMesh/columnFvMesh/columnFvMesh.C b/src/finiteVolume/fvMesh/simplifiedFvMesh/columnFvMesh/columnFvMesh.C
index 6b8ec3cc44..801a05ea2d 100644
--- a/src/finiteVolume/fvMesh/simplifiedFvMesh/columnFvMesh/columnFvMesh.C
+++ b/src/finiteVolume/fvMesh/simplifiedFvMesh/columnFvMesh/columnFvMesh.C
@@ -64,7 +64,7 @@ bool Foam::simplifiedMeshes::columnFvMeshInfo::setPatchEntries
     (
         "boundary",
         localInstance_,
-        polyMesh::regionName(regionName_)/polyMesh::meshSubDir,
+        polyMesh::meshDir(regionName_),
         runTime,
         IOobject::MUST_READ,
         IOobject::NO_WRITE,
@@ -209,7 +209,7 @@ void Foam::simplifiedMeshes::columnFvMeshInfo::initialise(const Time& runTime)
         (
             "points",
             localInstance_,
-            polyMesh::regionName(regionName_)/polyMesh::meshSubDir,
+            polyMesh::meshDir(regionName_),
             runTime,
             IOobject::MUST_READ,
             IOobject::NO_WRITE,
@@ -413,7 +413,7 @@ Foam::simplifiedMeshes::columnFvMeshInfo::columnFvMeshInfo
     (
         runTime.findInstance
         (
-            polyMesh::regionName(regionName_)/polyMesh::meshSubDir,
+            polyMesh::meshDir(regionName_),
             "boundary",
             IOobject::READ_IF_PRESENT
         )
diff --git a/src/functionObjects/field/externalCoupled/externalCoupled.C b/src/functionObjects/field/externalCoupled/externalCoupled.C
index 9ea75ad387..9506d85ac3 100644
--- a/src/functionObjects/field/externalCoupled/externalCoupled.C
+++ b/src/functionObjects/field/externalCoupled/externalCoupled.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2015-2022 OpenCFD Ltd.
+    Copyright (C) 2015-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -354,16 +354,9 @@ Foam::word Foam::functionObjects::externalCoupled::compositeName
     }
     else if (regionNames.size() == 1)
     {
-        if (regionNames[0] == polyMesh::defaultRegion)
-        {
-            // For compatibility with single region cases
-            // - suppress single region name
-            return word::null;
-        }
-        else
-        {
-            return regionNames[0];
-        }
+        // For compatibility with single region cases
+        // - suppress single region name
+        return polyMesh::regionName(regionNames[0]);
     }
 
     // Enforce lexical ordering
diff --git a/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C b/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C
index 2e32c900ad..88b9ad42da 100644
--- a/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C
+++ b/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C
@@ -3755,7 +3755,7 @@ void Foam::meshRefinement::removeFiles(const polyMesh& mesh)
     (
         "dummy",
         mesh.facesInstance(),
-        mesh.meshSubDir,
+        polyMesh::meshSubDir,
         mesh
     );
     fileName setsDir(io.path());
diff --git a/src/meshTools/topoSet/topoSets/topoSet.C b/src/meshTools/topoSet/topoSets/topoSet.C
index f83680e0e8..177fb22b46 100644
--- a/src/meshTools/topoSet/topoSets/topoSet.C
+++ b/src/meshTools/topoSet/topoSets/topoSet.C
@@ -136,7 +136,7 @@ Foam::fileName Foam::topoSet::localPath
     const word& name
 )
 {
-    return mesh.facesInstance()/mesh.dbDir()/polyMesh::meshSubDir/"sets"/name;
+    return mesh.facesInstance()/mesh.meshDir()/"sets"/name;
 }
 
 
@@ -327,7 +327,7 @@ Foam::IOobject Foam::topoSet::findIOobject
         name,
         mesh.time().findInstance
         (
-            mesh.dbDir()/polyMesh::meshSubDir/"sets",
+            mesh.meshDir()/"sets",
             word::null,
             IOobject::READ_IF_PRESENT,
             mesh.facesInstance()
@@ -628,7 +628,7 @@ void Foam::topoSet::removeFiles(const polyMesh& mesh)
     (
         "dummy",
         mesh.facesInstance(),
-        mesh.meshSubDir/"sets",
+        polyMesh::meshSubDir/"sets",
         mesh
     );
     fileName setsDir(io.path());
diff --git a/src/sampling/surface/isoSurface/isoSurfacePoint.C b/src/sampling/surface/isoSurface/isoSurfacePoint.C
index c0609efa83..464af60d82 100644
--- a/src/sampling/surface/isoSurface/isoSurfacePoint.C
+++ b/src/sampling/surface/isoSurface/isoSurfacePoint.C
@@ -1362,7 +1362,7 @@ Foam::isoSurfacePoint::isoSurfacePoint
         (
             "C",
             fvmesh.pointsInstance(),
-            fvmesh.meshSubDir,
+            polyMesh::meshSubDir,
             fvmesh,
             IOobject::NO_READ,
             IOobject::NO_WRITE,