diff --git a/pkgs/development/ocaml-modules/monolith/default.nix b/pkgs/development/ocaml-modules/monolith/default.nix
new file mode 100644
index 000000000000..a5945600d140
--- /dev/null
+++ b/pkgs/development/ocaml-modules/monolith/default.nix
@@ -0,0 +1,36 @@
+{
+  lib,
+  buildDunePackage,
+  fetchFromGitLab,
+  afl-persistent,
+  pprint,
+  version ? "20250314",
+}:
+
+buildDunePackage {
+  pname = "monolith";
+  inherit version;
+
+  minimalOCamlVersion = "4.12";
+
+  src = fetchFromGitLab {
+    domain = "gitlab.inria.fr";
+    owner = "fpottier";
+    repo = "monolith";
+    tag = version;
+    hash = "sha256-hIB3QSOLARumRgpUroTFUzSreHw7kMikGde+mB28sGM=";
+  };
+
+  propagatedBuildInputs = [
+    afl-persistent
+    pprint
+  ];
+
+  meta = {
+    description = "Facilities for testing an OCaml library";
+    homepage = "https://cambium.inria.fr/~fpottier/monolith/doc/monolith/Monolith/index.html";
+    changelog = "https://gitlab.inria.fr/fpottier/monolith/-/raw/${version}/CHANGES.md";
+    license = lib.licenses.lgpl3Plus;
+    maintainers = [ lib.maintainers.vbgl ];
+  };
+}
diff --git a/pkgs/top-level/ocaml-packages.nix b/pkgs/top-level/ocaml-packages.nix
index 70eb4408629b..a7d084561999 100644
--- a/pkgs/top-level/ocaml-packages.nix
+++ b/pkgs/top-level/ocaml-packages.nix
@@ -1252,6 +1252,8 @@ let
 
     mmap =  callPackage ../development/ocaml-modules/mmap { };
 
+    monolith = callPackage ../development/ocaml-modules/monolith { };
+
     mopsa = callPackage ../development/ocaml-modules/mopsa { };
 
     morbig = callPackage ../development/ocaml-modules/morbig { };