diff --git a/doc/release-notes/rl-2511.section.md b/doc/release-notes/rl-2511.section.md
index 4d1065a1e84c..e414ac7995b3 100644
--- a/doc/release-notes/rl-2511.section.md
+++ b/doc/release-notes/rl-2511.section.md
@@ -18,6 +18,8 @@
 
 - The minimum version of Nix required to evaluate Nixpkgs has been raised from 2.3 to 2.18.
 
+- `mono5` has been removed. Use `mono6` or `mono` instead.
+
 - The `offrss` package was removed due to lack of upstream maintenance since 2012. It's recommended for users to migrate to another RSS reader
 
 - GCC 9, 10, 11, and 12 have been removed, as they have reached end‐of‐life upstream and are no longer supported.
diff --git a/pkgs/development/compilers/mono/5.nix b/pkgs/development/compilers/mono/5.nix
deleted file mode 100644
index f8c58914b65c..000000000000
--- a/pkgs/development/compilers/mono/5.nix
+++ /dev/null
@@ -1,14 +0,0 @@
-{
-  callPackage,
-  fetchurl,
-}:
-
-callPackage ./generic.nix rec {
-  version = "5.20.1.34";
-  enableParallelBuilding = true;
-  env.NIX_CFLAGS_COMPILE = "-Wno-error=incompatible-pointer-types -Wno-error=implicit-function-declaration";
-  src = fetchurl {
-    url = "https://download.mono-project.com/sources/mono/mono-${version}.tar.bz2";
-    sha256 = "12vw5dkhmp1vk9l658pil8jiqirkpdsc5z8dm5mpj595yr6d94fd";
-  };
-}
diff --git a/pkgs/top-level/aliases.nix b/pkgs/top-level/aliases.nix
index 87e506f06df1..88ac017fa7a3 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
+  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
   mongodb-5_0 = throw "mongodb-5_0 has been removed, it's end of life since October 2024"; # Added 2024-10-01
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 04521e6c4eab..e081c6a11d58 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -5574,8 +5574,6 @@ with pkgs;
 
   mono4 = lowPrio (callPackage ../development/compilers/mono/4.nix { });
 
-  mono5 = callPackage ../development/compilers/mono/5.nix { };
-
   mono6 = callPackage ../development/compilers/mono/6.nix { };
 
   mozart2 = callPackage ../development/compilers/mozart {