diff --git a/pkgs/development/ocaml-modules/unionFind/default.nix b/pkgs/development/ocaml-modules/unionFind/default.nix
new file mode 100644
index 000000000000..aa1d5e82362b
--- /dev/null
+++ b/pkgs/development/ocaml-modules/unionFind/default.nix
@@ -0,0 +1,24 @@
+{ lib, fetchFromGitLab, buildDunePackage }:
+
+buildDunePackage rec {
+  pname = "unionFind";
+  version = "20220122";
+
+  useDune2 = true;
+  minimalOCamlVersion = "4.05";
+
+  src = fetchFromGitLab {
+    domain = "gitlab.inria.fr";
+    owner = "fpottier";
+    repo = pname;
+    rev = version;
+    sha256 = "sha256:0hdh56rbg8vfjd61q09cbmh8l5wmry5ykivg7gsm0v5ckkb3531r";
+  };
+
+  meta = {
+    description = "Implementations of the union-find data structure";
+    license = lib.licenses.lgpl2Only;
+    inherit (src.meta) homepage;
+    maintainers = [ lib.maintainers.vbgl ];
+  };
+}
diff --git a/pkgs/top-level/ocaml-packages.nix b/pkgs/top-level/ocaml-packages.nix
index 5c45168524f7..053e8173191c 100644
--- a/pkgs/top-level/ocaml-packages.nix
+++ b/pkgs/top-level/ocaml-packages.nix
@@ -1410,6 +1410,8 @@ let
 
     stdint = callPackage ../development/ocaml-modules/stdint { };
 
+    unionFind = callPackage ../development/ocaml-modules/unionFind { };
+
     unstrctrd = callPackage ../development/ocaml-modules/unstrctrd { };
 
     uucd = callPackage ../development/ocaml-modules/uucd { };