Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -5019,7 +5019,6 @@
 defm second_underscore : BooleanFFlag<"second-underscore">, Group<gfortran_Group>;
 defm sign_zero : BooleanFFlag<"sign-zero">, Group<gfortran_Group>;
 defm stack_arrays : BooleanFFlag<"stack-arrays">, Group<gfortran_Group>;
-defm underscoring : BooleanFFlag<"underscoring">, Group<gfortran_Group>;
 defm whole_file : BooleanFFlag<"whole-file">, Group<gfortran_Group>;
 
 // C++ SYCL options
@@ -5094,6 +5093,7 @@
 defm xor_operator : OptInFC1FFlag<"xor-operator", "Enable .XOR. as a synonym of .NEQV.">;
 defm logical_abbreviations : OptInFC1FFlag<"logical-abbreviations", "Enable logical abbreviations">;
 defm implicit_none : OptInFC1FFlag<"implicit-none", "No implicit typing allowed unless overridden by IMPLICIT statements">;
+defm underscoring : OptInFC1FFlag<"underscoring", "Appends one trailing underscore to external names">;
 
 def fno_automatic : Flag<["-"], "fno-automatic">, Group<f_Group>,
   HelpText<"Implies the SAVE attribute for non-automatic local objects in subprograms unless RECURSIVE">;
Index: clang/lib/Driver/ToolChains/Flang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Flang.cpp
+++ clang/lib/Driver/ToolChains/Flang.cpp
@@ -56,7 +56,8 @@
                   {options::OPT_module_dir, options::OPT_fdebug_module_writer,
                    options::OPT_fintrinsic_modules_path, options::OPT_pedantic,
                    options::OPT_std_EQ, options::OPT_W_Joined,
-                   options::OPT_fconvert_EQ, options::OPT_fpass_plugin_EQ});
+                   options::OPT_fconvert_EQ, options::OPT_fpass_plugin_EQ,
+                   options::OPT_funderscoring, options::OPT_fno_underscoring});
 }
 
 void Flang::addPicOptions(const ArgList &Args, ArgStringList &CmdArgs) const {
Index: flang/include/flang/Frontend/CodeGenOptions.def
===================================================================
--- flang/include/flang/Frontend/CodeGenOptions.def
+++ flang/include/flang/Frontend/CodeGenOptions.def
@@ -27,6 +27,7 @@
 CODEGENOPT(PICLevel, 2, 0) ///< PIC level of the LLVM module.
 CODEGENOPT(IsPIE, 1, 0) ///< PIE level is the same as PIC Level.
 
+CODEGENOPT(Underscoring, 1, 1)
 ENUM_CODEGENOPT(RelocationModel, llvm::Reloc::Model, 3, llvm::Reloc::PIC_) ///< Name of the relocation model to use.
 
 #undef CODEGENOPT
Index: flang/include/flang/Tools/CLOptions.inc
===================================================================
--- flang/include/flang/Tools/CLOptions.inc
+++ flang/include/flang/Tools/CLOptions.inc
@@ -191,7 +191,7 @@
 }
 
 #if !defined(FLANG_EXCLUDE_CODEGEN)
-inline void createDefaultFIRCodeGenPassPipeline(mlir::PassManager &pm) {
+inline void createDefaultFIRCodeGenPassPipeline(mlir::PassManager &pm, bool Underscoring = 1) {
   fir::addBoxedProcedurePass(pm);
   pm.addNestedPass<mlir::func::FuncOp>(
       fir::createAbstractResultOnFuncOptPass());
@@ -199,7 +199,8 @@
       fir::createAbstractResultOnGlobalOptPass());
   fir::addCodeGenRewritePass(pm);
   fir::addTargetRewritePass(pm);
-  fir::addExternalNameConversionPass(pm);
+  if (Underscoring)
+    fir::addExternalNameConversionPass(pm);
   fir::addFIRToLLVMPass(pm);
 }
 
@@ -208,13 +209,13 @@
 /// \param pm - MLIR pass manager that will hold the pipeline definition
 /// \param optLevel - optimization level used for creating FIR optimization
 ///   passes pipeline
-inline void createMLIRToLLVMPassPipeline(
-    mlir::PassManager &pm, llvm::OptimizationLevel optLevel = defaultOptLevel) {
+inline void createMLIRToLLVMPassPipeline(mlir::PassManager &pm,
+    llvm::OptimizationLevel optLevel = defaultOptLevel, bool Underscoring = 1) {
   // Add default optimizer pass pipeline.
   fir::createDefaultFIROptimizerPassPipeline(pm, optLevel);
 
   // Add codegen pass pipeline.
-  fir::createDefaultFIRCodeGenPassPipeline(pm);
+  fir::createDefaultFIRCodeGenPassPipeline(pm, Underscoring);
 }
 #undef FLANG_EXCLUDE_CODEGEN
 #endif
Index: flang/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- flang/lib/Frontend/CompilerInvocation.cpp
+++ flang/lib/Frontend/CompilerInvocation.cpp
@@ -160,6 +160,10 @@
     if (args.hasArg(clang::driver::options::OPT_pic_is_pie))
       opts.IsPIE = 1;
   }
+  if (args.hasFlag(clang::driver::options::OPT_fno_underscoring,
+                   clang::driver::options::OPT_funderscoring, false)) {
+    opts.Underscoring = 0;
+  }
 }
 
 /// Parses all target input arguments and populates the target
Index: flang/lib/Frontend/FrontendActions.cpp
===================================================================
--- flang/lib/Frontend/FrontendActions.cpp
+++ flang/lib/Frontend/FrontendActions.cpp
@@ -531,6 +531,7 @@
   auto opts = ci.getInvocation().getCodeGenOpts();
   llvm::OptimizationLevel level = mapToLevel(opts);
 
+  auto Underscoring = opts.Underscoring;
   fir::support::loadDialects(*mlirCtx);
   fir::support::registerLLVMTranslation(*mlirCtx);
 
@@ -541,7 +542,7 @@
   pm.enableVerifier(/*verifyPasses=*/true);
 
   // Create the pass pipeline
-  fir::createMLIRToLLVMPassPipeline(pm, level);
+  fir::createMLIRToLLVMPassPipeline(pm, level, Underscoring);
   mlir::applyPassManagerCLOptions(pm);
 
   // run the pass manager