diff --git a/pkgs/development/ocaml-modules/why3/default.nix b/pkgs/development/ocaml-modules/why3/default.nix
new file mode 100644
index 000000000000..3ce0f8bdfac3
--- /dev/null
+++ b/pkgs/development/ocaml-modules/why3/default.nix
@@ -0,0 +1,21 @@
+{ stdenv, ocaml, findlib, zarith, menhir, why3 }:
+
+let ocaml-version = stdenv.lib.getVersion ocaml; in
+
+assert stdenv.lib.versionAtLeast ocaml-version "4.01";
+
+stdenv.mkDerivation {
+  name = "ocaml-${why3.name}";
+
+  inherit (why3) src;
+
+  buildInputs = [ ocaml findlib zarith menhir ];
+
+  installTargets = "install-lib";
+
+  meta = {
+    inherit (why3.meta) license homepage;
+    platforms = ocaml.meta.platforms;
+    maintainers = with stdenv.lib.maintainers; [ vbgl ];
+  };
+}
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index ffc69199f33a..a3e0b9ab8e36 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -4740,6 +4740,10 @@ let
 
     vg = callPackage ../development/ocaml-modules/vg { };
 
+    why3 = callPackage ../development/ocaml-modules/why3 {
+      why3 = pkgs.why3;
+    };
+
     x509 = callPackage ../development/ocaml-modules/x509 { };
 
     xmlm = callPackage ../development/ocaml-modules/xmlm { };