Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -265,6 +265,8 @@
   space before parentheses. The custom options can be set using
   ``SpaceBeforeParensOptions``.
 
+- Improved Cpp20 Modules support.
+
 libclang
 --------
 
Index: clang/lib/Format/FormatToken.h
===================================================================
--- clang/lib/Format/FormatToken.h
+++ clang/lib/Format/FormatToken.h
@@ -76,6 +76,7 @@
   TYPE(LineComment)                                                            \
   TYPE(MacroBlockBegin)                                                        \
   TYPE(MacroBlockEnd)                                                          \
+  TYPE(ModulePartitionColon)                                                   \
   TYPE(NamespaceMacro)                                                         \
   TYPE(NonNullAssertion)                                                       \
   TYPE(NullCoalescingEqual)                                                    \
Index: clang/lib/Format/TokenAnnotator.cpp
===================================================================
--- clang/lib/Format/TokenAnnotator.cpp
+++ clang/lib/Format/TokenAnnotator.cpp
@@ -902,9 +902,13 @@
           break;
         }
       }
-      if (Contexts.back().ColonIsDictLiteral ||
-          Style.Language == FormatStyle::LK_Proto ||
-          Style.Language == FormatStyle::LK_TextProto) {
+      if (Line.First->isOneOf(Keywords.kw_module, Keywords.kw_import) ||
+          Line.First->startsSequence(tok::kw_export, Keywords.kw_module) ||
+          Line.First->startsSequence(tok::kw_export, Keywords.kw_import)) {
+        Tok->setType(TT_ModulePartitionColon);
+      } else if (Contexts.back().ColonIsDictLiteral ||
+                 Style.Language == FormatStyle::LK_Proto ||
+                 Style.Language == FormatStyle::LK_TextProto) {
         Tok->setType(TT_DictLiteral);
         if (Style.Language == FormatStyle::LK_TextProto) {
           if (FormatToken *Previous = Tok->getPreviousNonComment())
@@ -3244,6 +3248,7 @@
   auto HasExistingWhitespace = [&Right]() {
     return Right.WhitespaceRange.getBegin() != Right.WhitespaceRange.getEnd();
   };
+
   if (Right.Tok.getIdentifierInfo() && Left.Tok.getIdentifierInfo())
     return true; // Never ever merge two identifiers.
 
@@ -3253,6 +3258,25 @@
     return true;
 
   if (Style.isCpp()) {
+    // Space between import <iostream>.
+    // or import .....;
+    if (Left.is(Keywords.kw_import) && Right.isOneOf(tok::less, tok::ellipsis))
+      return true;
+    // No space between module :.
+    if (Left.isOneOf(Keywords.kw_module, Keywords.kw_import) &&
+        Right.is(TT_ModulePartitionColon))
+      return true;
+    // No space between import foo:bar but keep a space between import :bar;
+    if (Left.is(tok::identifier) && Right.is(TT_ModulePartitionColon))
+      return false;
+    // No space between :bar;
+    if (Left.is(TT_ModulePartitionColon) &&
+        Right.isOneOf(tok::identifier, tok::kw_private))
+      return false;
+    if (Left.is(tok::ellipsis) && Right.is(tok::identifier) &&
+        Line.First->is(Keywords.kw_import))
+      return false;
+
     if (Left.is(tok::kw_operator))
       return Right.is(tok::coloncolon);
     if (Right.is(tok::l_brace) && Right.is(BK_BracedInit) &&
Index: clang/lib/Format/UnwrappedLineParser.h
===================================================================
--- clang/lib/Format/UnwrappedLineParser.h
+++ clang/lib/Format/UnwrappedLineParser.h
@@ -110,6 +110,7 @@
   void parseCaseLabel();
   void parseSwitch();
   void parseNamespace();
+  void parseModuleImport();
   void parseNew();
   void parseAccessSpecifier();
   bool parseEnum();
Index: clang/lib/Format/UnwrappedLineParser.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineParser.cpp
+++ clang/lib/Format/UnwrappedLineParser.cpp
@@ -1052,6 +1052,36 @@
   return Tok->Previous && Tok->Previous->isOneOf(tok::l_paren, tok::comma);
 }
 
+void UnwrappedLineParser::parseModuleImport() {
+  nextToken();
+  do {
+    if (FormatTok->is(tok::colon)) {
+      FormatTok->setType(TT_ModulePartitionColon);
+    }
+    // Handle import <foo/bar.h> as we would an include statement
+    else if (FormatTok->is(tok::less)) {
+      nextToken();
+      while (FormatTok && FormatTok->isNot(tok::semi) &&
+             FormatTok->isNot(tok::greater)) {
+        // Mark tokens up to the trailing line comments as implicit string
+        // literals.
+        if (FormatTok->isNot(tok::comment) &&
+            !FormatTok->TokenText.startswith("//"))
+          FormatTok->setType(TT_ImplicitStringLiteral);
+        nextToken();
+      }
+    }
+    if (FormatTok->is(tok::semi)) {
+      nextToken();
+      break;
+    }
+    nextToken();
+  } while (!eof());
+
+  addUnwrappedLine();
+  return;
+}
+
 // readTokenWithJavaScriptASI reads the next token and terminates the current
 // line if JavaScript Automatic Semicolon Insertion must
 // happen between the current token and the next token.
@@ -1250,6 +1280,10 @@
         addUnwrappedLine();
         return;
       }
+      if (Style.isCpp()) {
+        parseModuleImport();
+        return;
+      }
     }
     if (Style.isCpp() &&
         FormatTok->isOneOf(Keywords.kw_signals, Keywords.kw_qsignals,
Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -22597,6 +22597,67 @@
   verifyFormat("auto(*p)() = f;");       // actually a declaration; TODO FIXME
 }
 
+TEST_F(FormatTest, Cpp20ModulesSupport) {
+  FormatStyle Style = getLLVMStyle();
+  Style.AllowShortBlocksOnASingleLine = FormatStyle::SBS_Never;
+  Style.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_None;
+
+  verifyFormat("export import foo;", Style);
+  verifyFormat("export import foo:bar;", Style);
+  verifyFormat("export import foo.bar;", Style);
+  verifyFormat("export import foo.bar:baz;", Style);
+  verifyFormat("export import :bar;", Style);
+  verifyFormat("export module foo:bar;", Style);
+  verifyFormat("export module foo;", Style);
+  verifyFormat("export module foo.bar;", Style);
+  verifyFormat("export module foo.bar:baz;", Style);
+  verifyFormat("export import <string_view>;", Style);
+
+  verifyFormat("export type_name var;", Style);
+  verifyFormat("template <class T> export using A = B<T>;", Style);
+  verifyFormat("export using A = B;", Style);
+  verifyFormat("export int func() {\n"
+               "  foo();\n"
+               "}",
+               Style);
+  verifyFormat("export struct {\n"
+               "  int foo;\n"
+               "};",
+               Style);
+  verifyFormat("export {\n"
+               "  int foo;\n"
+               "};",
+               Style);
+  verifyFormat("export export char const *hello() { return \"hello\"; }");
+
+  verifyFormat("import bar;", Style);
+  verifyFormat("import foo.bar;", Style);
+  verifyFormat("import foo:bar;", Style);
+  verifyFormat("import :bar;", Style);
+  verifyFormat("import <ctime>;", Style);
+  verifyFormat("import \"header\";", Style);
+
+  verifyFormat("module foo;", Style);
+  verifyFormat("module foo:bar;", Style);
+  verifyFormat("module foo.bar;", Style);
+  verifyFormat("module;", Style);
+
+  verifyFormat("export namespace hi {\n"
+               "const char *sayhi();\n"
+               "}",
+               Style);
+
+  verifyFormat("module :private;", Style);
+  verifyFormat("import <foo/bar.h>;", Style);
+  verifyFormat("import foo...bar;", Style);
+  verifyFormat("import ..........;", Style);
+  verifyFormat("module foo:private;", Style);
+  verifyFormat("import a", Style);
+  verifyFormat("module a", Style);
+  verifyFormat("export import a", Style);
+  verifyFormat("export module a", Style);
+}
+
 } // namespace
 } // namespace format
 } // namespace clang