diff --git a/pkgs/development/libraries/dotnetfx35/default.nix b/pkgs/development/libraries/dotnetfx35/default.nix
deleted file mode 100644
index 73e6fa003090..000000000000
--- a/pkgs/development/libraries/dotnetfx35/default.nix
+++ /dev/null
@@ -1,24 +0,0 @@
-{ stdenv }:
-
-let
-  windir = "/cygdrive/c/WINDOWS";
-in
-{
-  pkg = stdenv.mkDerivation rec {
-    pname = "dotnetfx";
-    version = "3.5";
-    src = "${windir}/Microsoft.NET/Framework/v${version}";
-    buildCommand = ''
-      mkdir -p $out/bin
-      ln -s $src/MSBuild.exe $out/bin
-    '';
-  };
-
-  assembly20Path = "/cygdrive/c/WINDOWS/Microsoft.NET/Framework/v2.0.50727";
-
-  wcfPath = "/cygdrive/c/WINDOWS/Microsoft.NET/Framework/v3.0/WINDOW~1";
-
-  referenceAssembly30Path = "/cygdrive/c/PROGRA~1/REFERE~1/Microsoft/Framework/v3.0";
-
-  referenceAssembly35Path = "/cygdrive/c/PROGRA~1/REFERE~1/Microsoft/Framework/v3.5";
-}
diff --git a/pkgs/development/libraries/dotnetfx40/default.nix b/pkgs/development/libraries/dotnetfx40/default.nix
deleted file mode 100644
index 7ca67f186ac8..000000000000
--- a/pkgs/development/libraries/dotnetfx40/default.nix
+++ /dev/null
@@ -1,24 +0,0 @@
-{ stdenv }:
-
-let
-  windir = "/cygdrive/c/WINDOWS";
-in
-{
-  pkg = stdenv.mkDerivation rec {
-    pname = "dotnetfx";
-    version = "4.0.30319";
-    src = "${windir}/Microsoft.NET/Framework/v${version}";
-    buildCommand = ''
-      mkdir -p $out/bin
-      ln -s $src/MSBuild.exe $out/bin
-    '';
-  };
-
-  assembly20Path = "/cygdrive/c/WINDOWS/Microsoft.NET/Framework/v2.0.50727";
-
-  wcfPath = "/cygdrive/c/WINDOWS/Microsoft.NET/Framework/v3.0/WINDOW~1";
-
-  referenceAssembly30Path = "/cygdrive/c/PROGRA~1/REFERE~1/Microsoft/Framework/v3.0";
-
-  referenceAssembly35Path = "/cygdrive/c/PROGRA~1/REFERE~1/Microsoft/Framework/v3.5";
-}
diff --git a/pkgs/top-level/aliases.nix b/pkgs/top-level/aliases.nix
index 25d37970b584..d394294c8125 100644
--- a/pkgs/top-level/aliases.nix
+++ b/pkgs/top-level/aliases.nix
@@ -567,6 +567,8 @@ mapAliases {
   dolphin-emu-beta = throw "'dolphin-emu-beta' has been renamed to/replaced by 'dolphin-emu'"; # Converted to throw 2025-10-27
   dontRecurseIntoAttrs = warnAlias "dontRecurseIntoAttrs has been removed from pkgs, use `lib.dontRecurseIntoAttrs` instead" lib.dontRecurseIntoAttrs; # Added 2025-10-30
   dotnetenv = throw "'dotnetenv' has been removed because it was unmaintained in Nixpkgs"; # Added 2025-07-11
+  dotnetfx35 = throw "'dotnetfx35' has been removed because it was unmaintained in Nixpkgs"; # Added 2026-01-27
+  dotnetfx40 = throw "'dotnetfx40' has been removed because it was unmaintained in Nixpkgs"; # Added 2026-01-27
   dotty = throw "'dotty' has been renamed to/replaced by 'scala_3'"; # Converted to throw 2025-10-27
   dovecot_fts_xapian = throw "'dovecot_fts_xapian' has been removed because it was unmaintained in Nixpkgs. Consider using dovecot-fts-flatcurve instead"; # Added 2025-08-16
   dsd = throw "dsd has been removed, as it was broken and lack of upstream maintenance"; # Added 2025-08-25
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 637032faf635..3f550a7644d4 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -2344,10 +2344,6 @@ with pkgs;
 
   diffutils = callPackage ../tools/text/diffutils { };
 
-  dotnetfx35 = callPackage ../development/libraries/dotnetfx35 { };
-
-  dotnetfx40 = callPackage ../development/libraries/dotnetfx40 { };
-
   drone = callPackage ../development/tools/continuous-integration/drone { };
   drone-oss = callPackage ../development/tools/continuous-integration/drone {
     enableUnfree = false;