diff --git a/clang/include/clang/Basic/Module.h b/clang/include/clang/Basic/Module.h
--- a/clang/include/clang/Basic/Module.h
+++ b/clang/include/clang/Basic/Module.h
@@ -106,9 +106,15 @@
     /// of header files.
     ModuleMapModule,
 
-    /// This is a C++ Modules TS module interface unit.
+    /// This is a C++20 module interface unit.
     ModuleInterfaceUnit,
 
+    /// This is a C++ 20 module partition interface.
+    ModulePartitionInterface,
+
+    /// This is a C++ 20 module partition implementation.
+    ModulePartitionImplementation,
+
     /// This is a fragment of the global module within some C++ module.
     GlobalModuleFragment,
 
@@ -150,7 +156,9 @@
 
   /// Does this Module scope describe part of the purview of a named C++ module?
   bool isModulePurview() const {
-    return Kind == ModuleInterfaceUnit || Kind == PrivateModuleFragment;
+    return Kind == ModuleInterfaceUnit || Kind == ModulePartitionInterface ||
+           Kind == ModulePartitionImplementation ||
+           Kind == PrivateModuleFragment;
   }
 
   /// Does this Module scope describe a fragment of the global module within
@@ -506,6 +514,9 @@
     Parent->SubModules.push_back(this);
   }
 
+  /// Is this a module partition.
+  bool isModulePartition() const { return Name.find(':') != std::string::npos; }
+
   /// Retrieve the full name of this module, including the path from
   /// its top-level module.
   /// \param AllowStringLiterals If \c true, components that might not be
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -1550,6 +1550,8 @@
     return nullptr;
 
   case Module::ModuleInterfaceUnit:
+  case Module::ModulePartitionInterface:
+  case Module::ModulePartitionImplementation:
     return M;
 
   case Module::GlobalModuleFragment: {
diff --git a/clang/lib/Sema/SemaModule.cpp b/clang/lib/Sema/SemaModule.cpp
--- a/clang/lib/Sema/SemaModule.cpp
+++ b/clang/lib/Sema/SemaModule.cpp
@@ -261,6 +261,8 @@
                                : ModuleScopes.back().Module->Kind) {
   case Module::ModuleMapModule:
   case Module::GlobalModuleFragment:
+  case Module::ModulePartitionImplementation:
+  case Module::ModulePartitionInterface:
     Diag(PrivateLoc, diag::err_private_module_fragment_not_module);
     return nullptr;
 
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -2674,7 +2674,7 @@
   Abbrev->Add(BitCodeAbbrevOp(SUBMODULE_DEFINITION));
   Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // ID
   Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Parent
-  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 2)); // Kind
+  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); // Kind
   Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // IsFramework
   Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // IsExplicit
   Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // IsSystem