diff --git a/flang/include/flang/Optimizer/Support/InternalNames.h b/flang/include/flang/Optimizer/Support/InternalNames.h
--- a/flang/include/flang/Optimizer/Support/InternalNames.h
+++ b/flang/include/flang/Optimizer/Support/InternalNames.h
@@ -41,7 +41,8 @@
     INTRINSIC_TYPE_DESC,
     PROCEDURE,
     TYPE_DESC,
-    VARIABLE
+    VARIABLE,
+    NAMELIST_GROUP
   };
 
   /// Components of an unparsed unique name
@@ -112,6 +113,11 @@
                                 llvm::Optional<llvm::StringRef> host,
                                 llvm::StringRef name);
 
+  /// Unique a namelist group name
+  static std::string doNamelistGroup(llvm::ArrayRef<llvm::StringRef> modules,
+                                     llvm::Optional<llvm::StringRef> host,
+                                     llvm::StringRef name);
+
   /// Entry point for the PROGRAM (called by the runtime)
   /// Can be overridden with the `--main-entry-name=<name>` option.
   static llvm::StringRef doProgramEntry();
diff --git a/flang/lib/Lower/Mangler.cpp b/flang/lib/Lower/Mangler.cpp
--- a/flang/lib/Lower/Mangler.cpp
+++ b/flang/lib/Lower/Mangler.cpp
@@ -114,6 +114,12 @@
                                                   symbolName);
             return fir::NameUniquer::doVariable(modNames, optHost, symbolName);
           },
+          [&](const Fortran::semantics::NamelistDetails &) {
+            auto modNames = moduleNames(ultimateSymbol);
+            auto optHost = hostName(ultimateSymbol);
+            return fir::NameUniquer::doNamelistGroup(modNames, optHost,
+                                                     symbolName);
+          },
           [&](const Fortran::semantics::CommonBlockDetails &) {
             return fir::NameUniquer::doCommonBlock(symbolName);
           },
diff --git a/flang/lib/Optimizer/Support/InternalNames.cpp b/flang/lib/Optimizer/Support/InternalNames.cpp
--- a/flang/lib/Optimizer/Support/InternalNames.cpp
+++ b/flang/lib/Optimizer/Support/InternalNames.cpp
@@ -205,6 +205,15 @@
   return result.append(toLower(name));
 }
 
+std::string
+fir::NameUniquer::doNamelistGroup(llvm::ArrayRef<llvm::StringRef> modules,
+                                  llvm::Optional<llvm::StringRef> host,
+                                  llvm::StringRef name) {
+  std::string result = prefix();
+  result.append(doModulesHost(modules, host)).append("G");
+  return result.append(toLower(name));
+}
+
 llvm::StringRef fir::NameUniquer::doProgramEntry() {
   if (mainEntryName.size())
     return mainEntryName;
@@ -279,6 +288,10 @@
         else
           kinds.push_back(readInt(uniq, i, i + 1, end));
         break;
+      case 'G':
+        nk = NameKind::NAMELIST_GROUP;
+        name = readName(uniq, i, i + 1, end);
+        break;
 
       default:
         assert(false && "unknown uniquing code");
diff --git a/flang/unittests/Optimizer/InternalNamesTest.cpp b/flang/unittests/Optimizer/InternalNamesTest.cpp
--- a/flang/unittests/Optimizer/InternalNamesTest.cpp
+++ b/flang/unittests/Optimizer/InternalNamesTest.cpp
@@ -162,6 +162,12 @@
   ASSERT_EQ(actual.str(), expectedMangledName);
 }
 
+TEST(InternalNamesTest, doNamelistGroup) {
+  std::string actual = NameUniquer::doNamelistGroup({"mod1"}, {}, "nlg");
+  std::string expectedMangledName = "_QMmod1Gnlg";
+  ASSERT_EQ(actual, expectedMangledName);
+}
+
 TEST(InternalNamesTest, deconstructTest) {
   std::pair actual = NameUniquer::deconstruct("_QBhello");
   auto expectedNameKind = NameUniquer::NameKind::COMMON;
@@ -208,6 +214,11 @@
   expectedNameKind = NameKind::DISPATCH_TABLE;
   expectedComponents = {{}, {}, "t", {}};
   validateDeconstructedName(actual, expectedNameKind, expectedComponents);
+
+  actual = NameUniquer::deconstruct("_QFmstartGmpitop");
+  expectedNameKind = NameKind::NAMELIST_GROUP;
+  expectedComponents = {{}, {"mstart"}, "mpitop", {}};
+  validateDeconstructedName(actual, expectedNameKind, expectedComponents);
 }
 
 // main() from gtest_main