diff --git a/pkgs/development/ocaml-modules/chacha/default.nix b/pkgs/development/ocaml-modules/chacha/default.nix
deleted file mode 100644
index f5d6c4c1008b..000000000000
--- a/pkgs/development/ocaml-modules/chacha/default.nix
+++ /dev/null
@@ -1,53 +0,0 @@
-{
-  lib,
-  buildDunePackage,
-  fetchFromGitHub,
-  fetchpatch,
-  ocaml,
-
-  alcotest,
-  cstruct,
-  mirage-crypto,
-}:
-
-buildDunePackage rec {
-  pname = "chacha";
-  version = "1.1.0";
-
-  src = fetchFromGitHub {
-    owner = "abeaumont";
-    repo = "ocaml-chacha";
-    rev = version;
-    hash = "sha256-PmeiFloU0k3SqOK1VjaliiCEzDzrzyMSasgnO5fJS1k=";
-  };
-
-  # Ensure compatibility with cstruct ≥ 6.1.0
-  patches = [
-    (fetchpatch {
-      url = "https://github.com/abeaumont/ocaml-chacha/commit/fbe4a0a808226229728a68f278adf370251196fd.patch";
-      sha256 = "sha256-y7X9toFDrgdv3qmFmUs7K7QS+Gy45rRLulKy48m7uqc=";
-    })
-  ];
-
-  propagatedBuildInputs = [
-    cstruct
-    mirage-crypto
-  ];
-
-  # alcotest isn't available for OCaml < 4.05 due to fmt
-  doCheck = lib.versionAtLeast ocaml.version "4.05";
-  checkInputs = [ alcotest ];
-
-  meta = {
-    homepage = "https://github.com/abeaumont/ocaml-chacha";
-    description = "ChaCha20, ChaCha12 and ChaCha8 encryption functions, in OCaml";
-    longDescription = ''
-      An OCaml implementation of ChaCha functions, both ChaCha20 and the reduced
-      ChaCha8 and ChaCha12 functions. The hot loop is implemented in C for efficiency
-      reasons.
-    '';
-    license = lib.licenses.bsd2;
-    maintainers = with lib.maintainers; [ fufexan ];
-    broken = true; # Not compatible with mirage-crypto ≥ 1.0
-  };
-}
diff --git a/pkgs/top-level/ocaml-packages.nix b/pkgs/top-level/ocaml-packages.nix
index 6463b9a32430..86e4c306066e 100644
--- a/pkgs/top-level/ocaml-packages.nix
+++ b/pkgs/top-level/ocaml-packages.nix
@@ -232,8 +232,6 @@ let
 
         cfstream = callPackage ../development/ocaml-modules/cfstream { };
 
-        chacha = callPackage ../development/ocaml-modules/chacha { };
-
         checkseum = callPackage ../development/ocaml-modules/checkseum { };
 
         chrome-trace = callPackage ../development/ocaml-modules/chrome-trace { };
@@ -2252,6 +2250,7 @@ let
       }
       // lib.optionalAttrs config.allowAliases {
         biocaml = throw "biocaml has been removed"; # 2025-06-04
+        chacha = throw "chacha has been removed because it has been marked as broken since at least November 2024. It is now vendored inside mirage-crypto, consider using that instead."; # Added 2025-10-11
         gd4o = throw "ocamlPackages.gd4o is not maintained, use ocamlPackages.gd instead";
         ocaml-vdom = throw "2023-10-09: ocamlPackages.ocaml-vdom was renamed to ocamlPackages.vdom";
       }