diff --git a/contrib/freestanding_lib/freestanding.py b/contrib/freestanding_lib/freestanding.py
index 4a02dea14..4e0a944f1 100755
--- a/contrib/freestanding_lib/freestanding.py
+++ b/contrib/freestanding_lib/freestanding.py
@@ -431,7 +431,7 @@ class Freestanding(object):
             external_xxhash: bool, xxh64_state: Optional[str],
             xxh64_prefix: Optional[str], rewritten_includes: [(str, str)],
             defs: [(str, Optional[str])], replaces: [(str, str)],
-            undefs: [str], excludes: [str], seds: [str],
+            undefs: [str], excludes: [str], seds: [str], spdx: bool,
     ):
         self._zstd_deps = zstd_deps
         self._mem = mem
@@ -446,6 +446,7 @@ class Freestanding(object):
         self._undefs = undefs
         self._excludes = excludes
         self._seds = seds
+        self._spdx = spdx
 
     def _dst_lib_file_paths(self):
         """
@@ -640,6 +641,27 @@ class Freestanding(object):
         for sed in self._seds:
             self._process_sed(sed)
 
+    def _process_spdx(self):
+        if not self._spdx:
+            return
+        self._log("Processing spdx")
+        SPDX_C = "// SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause\n"
+        SPDX_H_S = "/* SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause */\n"
+        for filepath in self._dst_lib_file_paths():
+            file = FileLines(filepath)
+            if file.lines[0] == SPDX_C or file.lines[0] == SPDX_H_S:
+                continue
+            for line in file.lines:
+                if "SPDX-License-Identifier" in line:
+                    raise RuntimeError(f"Unexpected SPDX license identifier: {file.filename} {repr(line)}")
+            if file.filename.endswith(".c"):
+                file.lines.insert(0, SPDX_C)
+            elif file.filename.endswith(".h") or file.filename.endswith(".S"):
+                file.lines.insert(0, SPDX_H_S)
+            else:
+                raise RuntimeError(f"Unexpected file extension: {file.filename}")
+            file.write()
+
 
 
     def go(self):
@@ -651,6 +673,7 @@ class Freestanding(object):
         self._rewrite_includes()
         self._replace_xxh64_prefix()
         self._process_seds()
+        self._process_spdx()
 
 
 def parse_optional_pair(defines: [str]) -> [(str, Optional[str])]:
@@ -689,6 +712,7 @@ def main(name, args):
     parser.add_argument("--xxh64-prefix", default=None, help="Alternate XXH64 function prefix (excluding _) e.g. --xxh64-prefix=xxh64")
     parser.add_argument("--rewrite-include", default=[], dest="rewritten_includes", action="append", help="Rewrite an include REGEX=NEW (e.g. '<stddef\\.h>=<linux/types.h>')")
     parser.add_argument("--sed", default=[], dest="seds", action="append", help="Apply a sed replacement. Format: `s/REGEX/FORMAT/[g]`. REGEX is a Python regex. FORMAT is a Python format string formatted by the regex dict.")
+    parser.add_argument("--spdx", action="store_true", help="Add SPDX License Identifiers")
     parser.add_argument("-D", "--define", default=[], dest="defs", action="append", help="Pre-define this macro (can be passed multiple times)")
     parser.add_argument("-U", "--undefine", default=[], dest="undefs", action="append", help="Pre-undefine this macro (can be passed multiple times)")
     parser.add_argument("-R", "--replace", default=[], dest="replaces", action="append", help="Pre-define this macro and replace the first ifndef block with its definition")
@@ -743,6 +767,7 @@ def main(name, args):
         args.undefs,
         args.excludes,
         args.seds,
+        args.spdx,
     ).go()
 
 if __name__ == "__main__":
diff --git a/contrib/linux-kernel/Makefile b/contrib/linux-kernel/Makefile
index 47a431740..38aa6f4f4 100644
--- a/contrib/linux-kernel/Makefile
+++ b/contrib/linux-kernel/Makefile
@@ -26,6 +26,7 @@ libzstd:
 		--rewrite-include '"(\.\./)?zstd_errors.h"=<linux/zstd_errors.h>' \
 		--sed 's,/\*\*\*,/* *,g' \
 		--sed 's,/\*\*,/*,g' \
+		--spdx \
 		-DZSTD_NO_INTRINSICS \
 		-DZSTD_NO_UNUSED_FUNCTIONS \
 		-DZSTD_LEGACY_SUPPORT=0 \