diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -2384,10 +2384,16 @@
 
   assert(FormatTok->is(tok::kw_if) && "'if' expected");
   nextToken();
-  if (FormatTok->isOneOf(tok::kw_constexpr, tok::identifier))
+  if (FormatTok->is(tok::exclaim))
     nextToken();
-  if (FormatTok->is(tok::l_paren))
-    parseParens();
+  if (FormatTok->is(tok::kw_consteval)) {
+    nextToken();
+  } else {
+    if (FormatTok->isOneOf(tok::kw_constexpr, tok::identifier))
+      nextToken();
+    if (FormatTok->is(tok::l_paren))
+      parseParens();
+  }
   HandleAttributes();
 
   bool NeedsUnwrappedLine = false;
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -583,6 +583,28 @@
                "  }\n"
                "g();");
 
+  verifyFormat("if consteval {\n}");
+  verifyFormat("if !consteval {\n}");
+  verifyFormat("if consteval {\n} else {\n}");
+  verifyFormat("if !consteval {\n} else {\n}");
+  verifyFormat("if consteval {\n"
+               "  f();\n"
+               "}");
+  verifyFormat("if !consteval {\n"
+               "  f();\n"
+               "}");
+  verifyFormat("if consteval {\n"
+               "  f();\n"
+               "} else {\n"
+               "  g();\n"
+               "}");
+  verifyFormat("if CONSTEVAL {\n"
+               "  f();\n"
+               "}");
+  verifyFormat("if !CONSTEVAL {\n"
+               "  f();\n"
+               "}");
+
   verifyFormat("if (a)\n"
                "  g();");
   verifyFormat("if (a) {\n"