diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -661,7 +661,7 @@
     HelpText<"Restrict all prior -I flags to double-quoted inclusion and "
              "remove current directory from include path">;
 def I : JoinedOrSeparate<["-"], "I">, Group<I_Group>,
-    Flags<[CC1Option,CC1AsOption]>, MetaVarName<"<dir>">,
+    Flags<[CC1Option,CC1AsOption,FlangOption,FC1Option]>, MetaVarName<"<dir>">,
     HelpText<"Add directory to include search path. If there are multiple -I "
              "options, these directories are searched in the order they are "
              "given before the standard system directories are searched. "
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -72,6 +72,8 @@
   }
   Args.ClaimAllArgs(options::OPT_D);
 
+  Args.AddAllArgs(CmdArgs, options::OPT_I);
+
   if (Output.isFilename()) {
     CmdArgs.push_back("-o");
     CmdArgs.push_back(Output.getFilename());
diff --git a/flang/include/flang/Frontend/PreprocessorOptions.h b/flang/include/flang/Frontend/PreprocessorOptions.h
--- a/flang/include/flang/Frontend/PreprocessorOptions.h
+++ b/flang/include/flang/Frontend/PreprocessorOptions.h
@@ -10,6 +10,7 @@
 class PreprocessorOptions {
 public:
   std::vector<std::pair<std::string, bool /*isUndef*/>> Macros;
+  std::vector<std::string> SearchDirectoriesFromI;
 
 public:
   PreprocessorOptions() {}
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -165,6 +165,10 @@
       opts.addMacroUndef(A->getValue());
     }
   }
+
+  // Add the ordered list of -I's.
+  for (const auto *A : args.filtered(clang::driver::options::OPT_I))
+    opts.SearchDirectoriesFromI.emplace_back(A->getValue());
 }
 
 bool CompilerInvocation::CreateFromArgs(CompilerInvocation &res,
@@ -237,10 +241,15 @@
   auto &fortranOptions = fortranOpts();
   const auto &preprocessorOptions = preprocessorOpts();
 
-  // These defaults are based on the defaults in f18/f18.cpp.
-  std::vector<std::string> searchDirectories{"."s};
-  fortranOptions.searchDirectories = searchDirectories;
   fortranOptions.isFixedForm = false;
 
   collectMacroDefinitions(fortranOptions, preprocessorOptions);
+
+  // These defaults are based on the defaults in f18/f18.cpp.
+  std::vector<std::string> searchDirectories{"."s};
+  for (const auto &searchDirectoryFromI :
+      preprocessorOptions.SearchDirectoriesFromI) {
+    searchDirectories.emplace_back(searchDirectoryFromI);
+  }
+  fortranOptions.searchDirectories = searchDirectories;
 }