diff --git a/build_defs.bzl b/build_defs.bzl
--- a/build_defs.bzl
+++ b/build_defs.bzl
@@ -188,7 +188,10 @@
     We need this for things like `struct timespec` that are not in c99, but
     are part of POSIX 1003.1b-1993."""
 
-    return ["_DARWIN_C_SOURCE=1", "_POSIX_C_SOURCE=199309L"]
+    return select({
+        "@platforms//os:freebsd": [],
+        "//conditions:default": ["_DARWIN_C_SOURCE=1", "_POSIX_C_SOURCE=199309L"],
+    })
 
 def xnnpack_test_deps_for_library():
     """Depencies needed for a library to use gunit."""
@@ -349,6 +352,7 @@
         }),
         copts = copts + select({
             "//build_config:linux_k8": gcc_x86_copts,
+            "//build_config:freebsd_x86_64": gcc_x86_copts,
             "//build_config:linux_arm": aarch32_copts,
             "//build_config:linux_armeabi": aarch32_copts,
             "//build_config:linux_armhf": aarch32_copts,
diff --git a/src/memory.c b/src/memory.c
--- a/src/memory.c
+++ b/src/memory.c
@@ -28,6 +28,10 @@
 #include <errno.h>
 #if XNN_HAS_MMAP
 #include <sys/mman.h>
+#endif
+/* FreeBSD uses MAP_ANON; provide MAP_ANONYMOUS alias for portability. */
+#if defined(__FreeBSD__) && !defined(MAP_ANONYMOUS)
+#define MAP_ANONYMOUS MAP_ANON
 #endif
 #include <unistd.h>
 #endif  // XNN_PLATFORM_WINDOWS
diff --git a/build_config/BUILD.bazel b/build_config/BUILD.bazel
--- a/build_config/BUILD.bazel
+++ b/build_config/BUILD.bazel
@@ -351,6 +351,11 @@
     ],
 )
 
+config_setting(
+    name = "freebsd_x86_64",
+    values = {"cpu": "freebsd"},
+)
+
 selects.config_setting_group(
     name = "x86",
     match_any = [
@@ -358,6 +363,7 @@
         ":android_x86_64",
         ":ios_x86_64",
         ":linux_k8",
+        ":freebsd_x86_64",
         ":macos_x86_64",
         ":macos_x86_64_legacy",
         ":tvos_x86_64",
@@ -376,6 +382,7 @@
         ":android_x86_64",
         ":ios_x86_64",
         ":linux_k8",
+        ":freebsd_x86_64",
         ":macos_x86_64",
         ":macos_x86_64_legacy",
         ":tvos_x86_64",