Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -228,6 +228,8 @@
   `const` `volatile` `static` `inline` `constexpr` `restrict`
   to be controlled relative to the `type`.
 
+- 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())
@@ -3214,6 +3218,17 @@
   if (Right.Tok.getIdentifierInfo() && Left.Tok.getIdentifierInfo())
     return true; // Never ever merge two identifiers.
   if (Style.isCpp()) {
+    // Space between import <iostream>.
+    if (Left.is(Keywords.kw_import) && Right.is(tok::less))
+      return true;
+    // No space between import foo:bar but keep a space between import :bar;
+    if (Left.is(tok::identifier) && !Left.is(Keywords.kw_import) &&
+        Right.is(TT_ModulePartitionColon))
+      return false;
+    // No space between :bar;
+    if (Left.is(TT_ModulePartitionColon) && Right.is(tok::identifier))
+      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.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineParser.cpp
+++ clang/lib/Format/UnwrappedLineParser.cpp
@@ -1250,6 +1250,21 @@
         addUnwrappedLine();
         return;
       }
+      if (Style.isCpp()) {
+        nextToken();
+        while (FormatTok) {
+          if (FormatTok->is(tok::colon)) {
+            FormatTok->setType(TT_ModulePartitionColon);
+          }
+          if (FormatTok->is(tok::semi)) {
+            nextToken();
+            break;
+          }
+          nextToken();
+        }
+        addUnwrappedLine();
+        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
@@ -22397,6 +22397,28 @@
   EXPECT_EQ(Code, format(Code, Style));
 }
 
+TEST_F(FormatTest, Cpp20ModulesSupport) {
+  FormatStyle Style = getLLVMStyle();
+
+  verifyFormat("export import foo:bar;", Style);
+  verifyFormat("export import :bar;", Style);
+  verifyFormat("export module foo:bar;", Style);
+  verifyFormat("export module foo;", Style);
+
+  verifyFormat("import foo:bar;", Style);
+  verifyFormat("import :bar;", Style);
+  verifyFormat("import bar;", Style);
+  verifyFormat("import <ctime>;", Style);
+
+  verifyFormat("module foo;", Style);
+  verifyFormat("module foo:bar;", Style);
+
+  verifyFormat("export namespace hi {\n"
+               "const char *sayhi();\n"
+               "}",
+               Style);
+}
+
 } // namespace
 } // namespace format
 } // namespace clang