Index: clang-tidy/modernize/RawStringLiteralCheck.cpp
===================================================================
--- clang-tidy/modernize/RawStringLiteralCheck.cpp
+++ clang-tidy/modernize/RawStringLiteralCheck.cpp
@@ -65,6 +65,13 @@
                                     33)) != StringRef::npos)
     return false;
 
+  // Don't replace chars from upper ASCII (>0x7F) as they can represent UTF-8
+  // or be supported by specific code pages only.
+  if (Bytes.find_if([](char C) {
+        return static_cast<unsigned char>(C) > 0x7Fu;
+      }) != StringRef::npos)
+    return false;
+
   CharSourceRange CharRange = Lexer::makeFileCharRange(
       CharSourceRange::getTokenRange(Literal->getSourceRange()),
       *Result.SourceManager, Result.Context->getLangOpts());
Index: test/clang-tidy/modernize-raw-string-literal.cpp
===================================================================
--- test/clang-tidy/modernize-raw-string-literal.cpp
+++ test/clang-tidy/modernize-raw-string-literal.cpp
@@ -40,6 +40,8 @@
 char const *const Us("goink\\\037");
 char const *const HexNonPrintable("\\\x03");
 char const *const Delete("\\\177");
+char const *const MultibyteSnowman("\xE2\x98\x83");
+// CHECK-FIXES: {{^}}char const *const MultibyteSnowman("\xE2\x98\x83");{{$}}
 
 char const *const TrailingSpace("A line \\with space. \n");
 char const *const TrailingNewLine("A single \\line.\n");