diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -3425,7 +3425,7 @@
   if (Opts.OpenMP && !Opts.OpenMPSimd) {
     GenerateArg(Args, OPT_fopenmp, SA);
 
-    if (Opts.OpenMP != 50)
+    if (Opts.OpenMP != 51)
       GenerateArg(Args, OPT_fopenmp_version_EQ, Twine(Opts.OpenMP), SA);
 
     if (!Opts.OpenMPUseTLS)
@@ -3441,7 +3441,7 @@
   if (Opts.OpenMPSimd) {
     GenerateArg(Args, OPT_fopenmp_simd, SA);
 
-    if (Opts.OpenMP != 50)
+    if (Opts.OpenMP != 51)
       GenerateArg(Args, OPT_fopenmp_version_EQ, Twine(Opts.OpenMP), SA);
   }
 
@@ -3816,7 +3816,7 @@
   }
 
   // Check if -fopenmp is specified and set default version to 5.0.
-  Opts.OpenMP = Args.hasArg(OPT_fopenmp) ? 50 : 0;
+  Opts.OpenMP = Args.hasArg(OPT_fopenmp) ? 51 : 0;
   // Check if -fopenmp-simd is specified.
   bool IsSimdSpecified =
       Args.hasFlag(options::OPT_fopenmp_simd, options::OPT_fno_openmp_simd,
@@ -3836,7 +3836,7 @@
   if (Opts.OpenMP || Opts.OpenMPSimd) {
     if (int Version = getLastArgIntValue(
             Args, OPT_fopenmp_version_EQ,
-            (IsSimdSpecified || IsTargetSpecified) ? 50 : Opts.OpenMP, Diags))
+            (IsSimdSpecified || IsTargetSpecified) ? 51 : Opts.OpenMP, Diags))
       Opts.OpenMP = Version;
     // Provide diagnostic when a given target is not expected to be an OpenMP
     // device or host.
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -1248,16 +1248,15 @@
     case 45:
       Builder.defineMacro("_OPENMP", "201511");
       break;
-    case 51:
-      Builder.defineMacro("_OPENMP", "202011");
+    case 50:
+      Builder.defineMacro("_OPENMP", "201811");
       break;
     case 52:
       Builder.defineMacro("_OPENMP", "202111");
       break;
-    case 50:
-    default:
-      // Default version is OpenMP 5.0
-      Builder.defineMacro("_OPENMP", "201811");
+    default: // case 51:
+      // Default version is OpenMP 5.1
+      Builder.defineMacro("_OPENMP", "202011");
       break;
     }
   }