diff --git a/pkgs/by-name/mo/mono-addins/package.nix b/pkgs/by-name/mo/mono-addins/package.nix
deleted file mode 100644
index e20614c683ec..000000000000
--- a/pkgs/by-name/mo/mono-addins/package.nix
+++ /dev/null
@@ -1,47 +0,0 @@
-{
-  lib,
-  stdenv,
-  fetchFromGitHub,
-  autoreconfHook,
-  pkg-config,
-  mono4,
-  gtk-sharp-2_0,
-}:
-
-stdenv.mkDerivation rec {
-  pname = "mono-addins";
-  version = "1.3.3";
-
-  src = fetchFromGitHub {
-    owner = "mono";
-    repo = "mono-addins";
-
-    rev = "mono-addins-${version}";
-    sha256 = "018g3bd8afjc39h22h2j5r6ldsdn08ynx7wg889gdvnxg3hrxgl2";
-  };
-
-  nativeBuildInputs = [
-    pkg-config
-    autoreconfHook
-  ];
-
-  # Use msbuild when https://github.com/NixOS/nixpkgs/pull/43680 is merged
-  buildInputs = [
-    mono4
-    gtk-sharp-2_0
-  ];
-
-  dontStrip = true;
-
-  meta = with lib; {
-    homepage = "https://www.mono-project.com/archived/monoaddins/";
-    description = "Generic framework for creating extensible applications";
-    mainProgram = "mautil";
-    longDescription = ''
-      Mono.Addins is a generic framework for creating extensible applications,
-      and for creating libraries which extend those applications.
-    '';
-    platforms = platforms.linux;
-    license = licenses.mit;
-  };
-}
diff --git a/pkgs/top-level/aliases.nix b/pkgs/top-level/aliases.nix
index 88ac017fa7a3..4e0255d32e2a 100644
--- a/pkgs/top-level/aliases.nix
+++ b/pkgs/top-level/aliases.nix
@@ -1563,6 +1563,7 @@ mapAliases {
   mod_spkac = throw "'mod_spkac' has been renamed to/replaced by 'apacheHttpdPackages.mod_spkac'"; # Converted to throw 2024-10-17
   mod_pkcs12 = throw "'mod_pkcs12' has been renamed to/replaced by 'apacheHttpdPackages.mod_pkcs12'"; # Converted to throw 2024-10-17
   mod_timestamp = throw "'mod_timestamp' has been renamed to/replaced by 'apacheHttpdPackages.mod_timestamp'"; # Converted to throw 2024-10-17
+  mono-addins = throw "mono-addins has been removed due to its dependency on the removed mono4. Consider alternative frameworks or migrate to newer .NET technologies."; # Added 2025-08-25
   mono5 = mono6; # Added 2025-08-25
   monero = throw "'monero' has been renamed to/replaced by 'monero-cli'"; # Converted to throw 2024-10-17
   mongodb-4_4 = throw "mongodb-4_4 has been removed, it's end of life since April 2024"; # Added 2024-04-11
diff --git a/pkgs/top-level/dotnet-packages.nix b/pkgs/top-level/dotnet-packages.nix
index 37a7a298b088..4d8f833d4d18 100644
--- a/pkgs/top-level/dotnet-packages.nix
+++ b/pkgs/top-level/dotnet-packages.nix
@@ -138,38 +138,6 @@ let
 
     # SOURCE PACKAGES
 
-    MonoAddins = buildDotnetPackage rec {
-      pname = "Mono.Addins";
-      version = "1.2";
-
-      xBuildFiles = [
-        "Mono.Addins/Mono.Addins.csproj"
-        "Mono.Addins.Setup/Mono.Addins.Setup.csproj"
-        "Mono.Addins.Gui/Mono.Addins.Gui.csproj"
-        "Mono.Addins.CecilReflector/Mono.Addins.CecilReflector.csproj"
-      ];
-      outputFiles = [ "bin/*" ];
-
-      src = fetchFromGitHub {
-        owner = "mono";
-        repo = "mono-addins";
-        rev = "mono-addins-${version}";
-        sha256 = "1hnn0a2qsjcjprsxas424bzvhsdwy0yc2jj5xbp698c0m9kfk24y";
-      };
-
-      buildInputs = [ pkgs.gtk-sharp-2_0 ];
-
-      meta = {
-        description = "Generic framework for creating extensible applications";
-        homepage = "https://www.mono-project.com/Mono.Addins";
-        longDescription = ''
-          A generic framework for creating extensible applications,
-          and for creating libraries which extend those applications.
-        '';
-        license = lib.licenses.mit;
-      };
-    };
-
     NewtonsoftJson = fetchNuGet {
       pname = "Newtonsoft.Json";
       version = "11.0.2";