diff --git a/flang/include/flang/Semantics/semantics.h b/flang/include/flang/Semantics/semantics.h
--- a/flang/include/flang/Semantics/semantics.h
+++ b/flang/include/flang/Semantics/semantics.h
@@ -185,7 +185,7 @@
   std::optional<parser::CharBlock> location_;
   std::vector<std::string> searchDirectories_;
   std::string moduleDirectory_{"."s};
-  std::string moduleFileSuffix_{".mod"};
+  std::string moduleFileSuffix_{".f18.mod"};
   bool warnOnNonstandardUsage_{false};
   bool warningsAreErrors_{false};
   bool debugModuleWriter_{false};
diff --git a/flang/test/Driver/Inputs/basictestmoduleone.mod b/flang/test/Driver/Inputs/basictestmoduleone.f18.mod
rename from flang/test/Driver/Inputs/basictestmoduleone.mod
rename to flang/test/Driver/Inputs/basictestmoduleone.f18.mod
diff --git a/flang/test/Driver/Inputs/ieee_arithmetic.mod b/flang/test/Driver/Inputs/ieee_arithmetic.f18.mod
rename from flang/test/Driver/Inputs/ieee_arithmetic.mod
rename to flang/test/Driver/Inputs/ieee_arithmetic.f18.mod
diff --git a/flang/test/Driver/Inputs/iso_fortran_env.mod b/flang/test/Driver/Inputs/iso_fortran_env.f18.mod
rename from flang/test/Driver/Inputs/iso_fortran_env.mod
rename to flang/test/Driver/Inputs/iso_fortran_env.f18.mod
diff --git a/flang/test/Driver/Inputs/module-dir/basictestmoduleone.mod b/flang/test/Driver/Inputs/module-dir/basictestmoduleone.f18.mod
rename from flang/test/Driver/Inputs/module-dir/basictestmoduleone.mod
rename to flang/test/Driver/Inputs/module-dir/basictestmoduleone.f18.mod
diff --git a/flang/test/Driver/Inputs/module-dir/basictestmoduletwo.mod b/flang/test/Driver/Inputs/module-dir/basictestmoduletwo.f18.mod
rename from flang/test/Driver/Inputs/module-dir/basictestmoduletwo.mod
rename to flang/test/Driver/Inputs/module-dir/basictestmoduletwo.f18.mod
diff --git a/flang/test/Driver/fdefault.f90 b/flang/test/Driver/fdefault.f90
--- a/flang/test/Driver/fdefault.f90
+++ b/flang/test/Driver/fdefault.f90
@@ -5,22 +5,22 @@
 ! FLANG DRIVER (flang-new)
 !--------------------------
 ! RUN: rm -rf %t/dir-flang-new  && mkdir -p %t/dir-flang-new && %flang -fsyntax-only -module-dir %t/dir-flang-new %s  2>&1
-! RUN: cat %t/dir-flang-new/m.mod | FileCheck %s --check-prefix=NOOPTION
+! RUN: cat %t/dir-flang-new/m.f18.mod | FileCheck %s --check-prefix=NOOPTION
 ! RUN: rm -rf %t/dir-flang-new  && mkdir -p %t/dir-flang-new && %flang -fsyntax-only -fdefault-real-8 -module-dir %t/dir-flang-new %s  2>&1
-! RUN: cat %t/dir-flang-new/m.mod | FileCheck %s --check-prefix=REAL8
+! RUN: cat %t/dir-flang-new/m.f18.mod | FileCheck %s --check-prefix=REAL8
 ! RUN: rm -rf %t/dir-flang-new  && mkdir -p %t/dir-flang-new && %flang -fsyntax-only -fdefault-real-8 -fdefault-double-8 -module-dir %t/dir-flang-new %s  2>&1
-! RUN: cat %t/dir-flang-new/m.mod | FileCheck %s --check-prefix=DOUBLE8
+! RUN: cat %t/dir-flang-new/m.f18.mod | FileCheck %s --check-prefix=DOUBLE8
 ! RUN: not %flang -fsyntax-only -fdefault-double-8 %s  2>&1 | FileCheck %s --check-prefix=ERROR
 
 !-----------------------------------------
 ! FRONTEND FLANG DRIVER (flang-new -fc1)
 !-----------------------------------------
 ! RUN: rm -rf %t/dir-flang-new  && mkdir -p %t/dir-flang-new && %flang_fc1 -fsyntax-only -module-dir %t/dir-flang-new %s  2>&1
-! RUN: cat %t/dir-flang-new/m.mod | FileCheck %s --check-prefix=NOOPTION
+! RUN: cat %t/dir-flang-new/m.f18.mod | FileCheck %s --check-prefix=NOOPTION
 ! RUN: rm -rf %t/dir-flang-new  && mkdir -p %t/dir-flang-new && %flang_fc1 -fsyntax-only -fdefault-real-8 -module-dir %t/dir-flang-new %s  2>&1
-! RUN: cat %t/dir-flang-new/m.mod | FileCheck %s --check-prefix=REAL8
+! RUN: cat %t/dir-flang-new/m.f18.mod | FileCheck %s --check-prefix=REAL8
 ! RUN: rm -rf %t/dir-flang-new  && mkdir -p %t/dir-flang-new && %flang_fc1 -fsyntax-only -fdefault-real-8 -fdefault-double-8 -module-dir %t/dir-flang-new %s  2>&1
-! RUN: cat %t/dir-flang-new/m.mod | FileCheck %s --check-prefix=DOUBLE8
+! RUN: cat %t/dir-flang-new/m.f18.mod | FileCheck %s --check-prefix=DOUBLE8
 ! RUN: not %flang_fc1 -fsyntax-only -fdefault-double-8 %s  2>&1 | FileCheck %s --check-prefix=ERROR
 
 !-----------------------------------------
diff --git a/flang/test/Driver/flarge-sizes.f90 b/flang/test/Driver/flarge-sizes.f90
--- a/flang/test/Driver/flarge-sizes.f90
+++ b/flang/test/Driver/flarge-sizes.f90
@@ -5,17 +5,17 @@
 ! FLANG DRIVER (flang-new)
 !--------------------------
 ! RUN: rm -rf %t/dir-flang-new  && mkdir -p %t/dir-flang-new && %flang -fsyntax-only -module-dir %t/dir-flang-new %s  2>&1
-! RUN: cat %t/dir-flang-new/m.mod | FileCheck %s --check-prefix=NOLARGE
+! RUN: cat %t/dir-flang-new/m.f18.mod | FileCheck %s --check-prefix=NOLARGE
 ! RUN: rm -rf %t/dir-flang-new  && mkdir -p %t/dir-flang-new && %flang -fsyntax-only -flarge-sizes -module-dir %t/dir-flang-new %s  2>&1
-! RUN: cat %t/dir-flang-new/m.mod | FileCheck %s --check-prefix=LARGE
+! RUN: cat %t/dir-flang-new/m.f18.mod | FileCheck %s --check-prefix=LARGE
 
 !-----------------------------------------
 ! FRONTEND FLANG DRIVER (flang-new -fc1)
 !-----------------------------------------
 ! RUN: rm -rf %t/dir-flang-new  && mkdir -p %t/dir-flang-new && %flang_fc1 -fsyntax-only -module-dir %t/dir-flang-new %s  2>&1
-! RUN: cat %t/dir-flang-new/m.mod | FileCheck %s --check-prefix=NOLARGE
+! RUN: cat %t/dir-flang-new/m.f18.mod | FileCheck %s --check-prefix=NOLARGE
 ! RUN: rm -rf %t/dir-flang-new  && mkdir -p %t/dir-flang-new && %flang_fc1 -fsyntax-only -flarge-sizes -module-dir %t/dir-flang-new %s  2>&1
-! RUN: cat %t/dir-flang-new/m.mod | FileCheck %s --check-prefix=LARGE
+! RUN: cat %t/dir-flang-new/m.f18.mod | FileCheck %s --check-prefix=LARGE
 
 !-----------------------------------------
 ! EXPECTED OUTPUT WITHOUT -flarge-sizes
diff --git a/flang/test/Driver/write-module.f90 b/flang/test/Driver/write-module.f90
--- a/flang/test/Driver/write-module.f90
+++ b/flang/test/Driver/write-module.f90
@@ -8,21 +8,21 @@
 !--------------------------
 ! RUN: rm -rf %t && mkdir -p %t/dir-flang
 ! RUN: cd %t && %flang -fsyntax-only -module-dir %t/dir-flang %s
-! RUN: ls %t/dir-flang/testmodule.mod && not ls %t/testmodule.mod
+! RUN: ls %t/dir-flang/testmodule.f18.mod && not ls %t/testmodule.f18.mod
 
 !---------------------------
 ! -J <dir> (i.e. with space)
 !---------------------------
 ! RUN: rm -rf %t && mkdir -p %t/dir-flang
 ! RUN: cd %t && %flang -fsyntax-only -J %t/dir-flang %s
-! RUN: ls %t/dir-flang/testmodule.mod && not ls %t/testmodule.mod
+! RUN: ls %t/dir-flang/testmodule.f18.mod && not ls %t/testmodule.f18.mod
 
 !------------------------------
 ! -J<dir> (i.e. without space)
 !------------------------------
 ! RUN: rm -rf %t && mkdir -p %t/dir-flang
 ! RUN: cd %t && %flang -fsyntax-only -J%t/dir-flang %s
-! RUN: ls %t/dir-flang/testmodule.mod && not ls %t/testmodule.mod
+! RUN: ls %t/dir-flang/testmodule.f18.mod && not ls %t/testmodule.f18.mod
 
 module testmodule
   type::t2
diff --git a/flang/test/Semantics/Inputs/modfile09-a.f90 b/flang/test/Semantics/Inputs/modfile09-a.f90
--- a/flang/test/Semantics/Inputs/modfile09-a.f90
+++ b/flang/test/Semantics/Inputs/modfile09-a.f90
@@ -6,7 +6,7 @@
   end interface
 end
 
-!Expect: m.mod
+!Expect: m.f18.mod
 !module m
 !integer(4)::m1_x
 !interface
diff --git a/flang/test/Semantics/Inputs/modfile09-b.f90 b/flang/test/Semantics/Inputs/modfile09-b.f90
--- a/flang/test/Semantics/Inputs/modfile09-b.f90
+++ b/flang/test/Semantics/Inputs/modfile09-b.f90
@@ -2,7 +2,7 @@
   integer s1_x
 end
 
-!Expect: m-s1.mod
+!Expect: m-s1.f18.mod
 !submodule(m) s1
 !integer(4)::s1_x
 !end
diff --git a/flang/test/Semantics/Inputs/modfile09-c.f90 b/flang/test/Semantics/Inputs/modfile09-c.f90
--- a/flang/test/Semantics/Inputs/modfile09-c.f90
+++ b/flang/test/Semantics/Inputs/modfile09-c.f90
@@ -2,7 +2,7 @@
   integer s2_x
 end
 
-!Expect: m-s2.mod
+!Expect: m-s2.f18.mod
 !submodule(m:s1) s2
 !integer(4)::s2_x
 !end
diff --git a/flang/test/Semantics/Inputs/modfile09-d.f90 b/flang/test/Semantics/Inputs/modfile09-d.f90
--- a/flang/test/Semantics/Inputs/modfile09-d.f90
+++ b/flang/test/Semantics/Inputs/modfile09-d.f90
@@ -2,7 +2,7 @@
   integer s3_x
 end
 
-!Expect: m-s3.mod
+!Expect: m-s3.f18.mod
 !submodule(m:s2) s3
 !integer(4)::s3_x
 !end
diff --git a/flang/test/Semantics/getsymbols02.f90 b/flang/test/Semantics/getsymbols02.f90
--- a/flang/test/Semantics/getsymbols02.f90
+++ b/flang/test/Semantics/getsymbols02.f90
@@ -10,5 +10,5 @@
 ! RUN: %flang_fc1 -fsyntax-only %S/Inputs/getsymbols02-a.f90
 ! RUN: %flang_fc1 -fsyntax-only %S/Inputs/getsymbols02-b.f90
 ! RUN: %flang_fc1 -fsyntax-only -fget-symbols-sources %s 2>&1 | FileCheck %s
-! CHECK: callget5: .{{[/\\]}}mm2b.mod,
-! CHECK: get5: .{{[/\\]}}mm2a.mod,
+! CHECK: callget5: .{{[/\\]}}mm2b.f18.mod,
+! CHECK: get5: .{{[/\\]}}mm2a.f18.mod,
diff --git a/flang/test/Semantics/resolve12.f90 b/flang/test/Semantics/resolve12.f90
--- a/flang/test/Semantics/resolve12.f90
+++ b/flang/test/Semantics/resolve12.f90
@@ -6,7 +6,7 @@
 end
 
 use m1
-!ERROR: Cannot read module file for module 'm2': Source file 'm2.mod' was not found
+!ERROR: Cannot read module file for module 'm2': Source file 'm2.f18.mod' was not found
 use m2
 !ERROR: 'sub' is not a module
 use sub
diff --git a/flang/test/Semantics/resolve26.f90 b/flang/test/Semantics/resolve26.f90
--- a/flang/test/Semantics/resolve26.f90
+++ b/flang/test/Semantics/resolve26.f90
@@ -16,10 +16,10 @@
 submodule(m1) s1
 end
 
-!ERROR: Cannot read module file for submodule 's1' of module 'm2': Source file 'm2-s1.mod' was not found
+!ERROR: Cannot read module file for submodule 's1' of module 'm2': Source file 'm2-s1.f18.mod' was not found
 submodule(m2:s1) s2
 end
 
-!ERROR: Cannot read module file for module 'm3': Source file 'm3.mod' was not found
+!ERROR: Cannot read module file for module 'm3': Source file 'm3.f18.mod' was not found
 submodule(m3:s1) s3
 end
diff --git a/flang/test/Semantics/test_modfile.sh b/flang/test/Semantics/test_modfile.sh
--- a/flang/test/Semantics/test_modfile.sh
+++ b/flang/test/Semantics/test_modfile.sh
@@ -6,8 +6,8 @@
 srcdir=$(dirname $0)
 source $srcdir/common.sh
 
-actual=$temp/actual.mod
-expect=$temp/expect.mod
+actual=$temp/actual.f18.mod
+expect=$temp/expect.f18.mod
 actual_files=$temp/actual_files
 prev_files=$temp/prev_files
 diffs=$temp/diffs
diff --git a/flang/tools/f18/CMakeLists.txt b/flang/tools/f18/CMakeLists.txt
--- a/flang/tools/f18/CMakeLists.txt
+++ b/flang/tools/f18/CMakeLists.txt
@@ -61,11 +61,3 @@
 add_custom_target(module_files ALL DEPENDS ${MODULE_FILES})
 
 install(TARGETS f18 DESTINATION bin)
-
-# This flang shell script will only work in a POSIX shell.
-if (NOT WIN32)
-  file(COPY ${CMAKE_CURRENT_SOURCE_DIR}/flang
-    DESTINATION ${CMAKE_BINARY_DIR}/bin
-    FILE_PERMISSIONS OWNER_EXECUTE OWNER_READ OWNER_WRITE)
-  install(PROGRAMS ${CMAKE_BINARY_DIR}/bin/flang DESTINATION bin)
-endif()
diff --git a/flang/tools/f18/f18.cpp b/flang/tools/f18/f18.cpp
--- a/flang/tools/f18/f18.cpp
+++ b/flang/tools/f18/f18.cpp
@@ -87,7 +87,7 @@
   std::string outputPath; // -o path
   std::vector<std::string> searchDirectories; // -I dir
   std::string moduleDirectory{"."s}; // -module dir
-  std::string moduleFileSuffix{".mod"}; // -moduleSuffix suff
+  std::string moduleFileSuffix{".f18.mod"}; // -moduleSuffix suff
   bool forcedForm{false}; // -Mfixed or -Mfree appeared
   bool warnOnNonstandardUsage{false}; // -Mstandard
   bool warningsAreErrors{false}; // -Werror
diff --git a/flang/tools/f18/flang b/flang/tools/f18/flang
deleted file mode 100644
--- a/flang/tools/f18/flang
+++ /dev/null
@@ -1,16 +0,0 @@
-#!/bin/bash
-#===-- tools/f18/flang.sh -----------------------------------------*- sh -*-===#
-#
-# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-# See https://llvm.org/LICENSE.txt for license information.
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-#
-#===------------------------------------------------------------------------===#
-
-wd=$(cd $(dirname "$0")/.. && pwd)
-opts="-module-suffix .f18.mod "
-if ! $wd/bin/f18 $opts "$@"
-then status=$?
-     echo flang: in $PWD, f18 failed with exit status $status: $wd/bin/f18 $opts "$@" >&2
-     exit $status
-fi