Index: clang/lib/Format/TokenAnnotator.cpp
===================================================================
--- clang/lib/Format/TokenAnnotator.cpp
+++ clang/lib/Format/TokenAnnotator.cpp
@@ -3225,7 +3225,10 @@
     return false;
   if (Left.is(tok::period) || Right.is(tok::period))
     return false;
-  if (Right.is(tok::hash) && Left.is(tok::identifier) && Left.TokenText == "L")
+  // u#str
+  if (Right.is(tok::hash) && Left.is(tok::identifier) &&
+      (Left.TokenText == "L" || Left.TokenText == "u" ||
+       Left.TokenText == "U" || Left.TokenText == "u8"))
     return false;
   if (Left.is(TT_TemplateCloser) && Left.MatchingParen &&
       Left.MatchingParen->Previous &&
Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -4342,6 +4342,9 @@
 
 TEST_F(FormatTest, HashInMacroDefinition) {
   EXPECT_EQ("#define A(c) L#c", format("#define A(c) L#c", getLLVMStyle()));
+  EXPECT_EQ("#define A(c) u#c", format("#define A(c) u#c", getLLVMStyle()));
+  EXPECT_EQ("#define A(c) U#c", format("#define A(c) U#c", getLLVMStyle()));
+  EXPECT_EQ("#define A(c) u8#c", format("#define A(c) u8#c", getLLVMStyle()));
   verifyFormat("#define A \\\n  b #c;", getLLVMStyleWithColumns(11));
   verifyFormat("#define A  \\\n"
                "  {        \\\n"