diff --git a/pkgs/development/tools/smlfmt/default.nix b/pkgs/development/tools/smlfmt/default.nix
new file mode 100644
index 000000000000..1475de94193d
--- /dev/null
+++ b/pkgs/development/tools/smlfmt/default.nix
@@ -0,0 +1,37 @@
+{ lib, stdenv, fetchFromGitHub, pkg-config, mlton }:
+
+stdenv.mkDerivation rec {
+  pname = "smlfmt";
+  version = "1.0.0";
+
+  src = fetchFromGitHub {
+    owner = "shwestrick";
+    repo = pname;
+    rev = "v${version}";
+    hash = "sha256-7CTfMiEvuOena5SOE0qKpFPq6ARxmkE6d+loznZNbC0=";
+  };
+
+  nativeBuildInputs = [ mlton ];
+
+  installPhase = ''
+    runHook preInstall
+    install -Dm755 -t $out/bin smlfmt
+    runHook postInstall
+  '';
+
+  meta = {
+    description = "A custom parser/auto-formatter for Standard ML";
+    longDescription = ''
+      A custom parser and code formatter for Standard ML, with helpful error messages.
+
+      Supports SML source files (.sml, .sig, .fun, etc.) as well as MLBasis
+      compilation files (.mlb) using MLton conventions, including MLBasis path
+      maps.
+    '';
+
+    license = lib.licenses.mit;
+    maintainers = with lib.maintainers; [ munksgaard ];
+    platforms = mlton.meta.platforms;
+    homepage = "https://github.com/shwestrick/smlfmt";
+  };
+}
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 967dcde1c9a5..6a8d3c1a90c8 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -15591,6 +15591,8 @@ with pkgs;
 
   shmig = callPackage ../development/tools/database/shmig { };
 
+  smlfmt = callPackage ../development/tools/smlfmt { };
+
   # smlnjBootstrap should be redundant, now that smlnj works on Darwin natively
   smlnjBootstrap = callPackage ../development/compilers/smlnj/bootstrap.nix { };
   smlnj = callPackage ../development/compilers/smlnj {