diff --git a/nixos/doc/manual/release-notes/rl-2105.xml b/nixos/doc/manual/release-notes/rl-2105.xml
index ca4b468e355..092068c3d3b 100644
--- a/nixos/doc/manual/release-notes/rl-2105.xml
+++ b/nixos/doc/manual/release-notes/rl-2105.xml
@@ -552,14 +552,16 @@ self: super:
    </listitem>
    <listitem>
     <para>
-     The default-version of <literal>nextcloud</literal> is <package>nextcloud20</package>.
+     The default-version of <literal>nextcloud</literal> is <package>nextcloud21</package>.
      Please note that it's <emphasis>not</emphasis> possible to upgrade <literal>nextcloud</literal>
      across multiple major versions! This means that it's e.g. not possible to upgrade
-     from <package>nextcloud18</package> to <package>nextcloud20</package> in a single deploy.
+     from <package>nextcloud18</package> to <package>nextcloud20</package> in a single deploy and
+     most <literal>20.09</literal> users will have to upgrade to <package>nextcloud20</package>
+     first.
     </para>
     <para>
      The package can be manually upgraded by setting <xref linkend="opt-services.nextcloud.package" />
-     to <package>nextcloud20</package>.
+     to <package>nextcloud21</package>.
     </para>
    </listitem>
    <listitem>
diff --git a/nixos/modules/services/web-apps/nextcloud.nix b/nixos/modules/services/web-apps/nextcloud.nix
index de1c67235f4..413db757357 100644
--- a/nixos/modules/services/web-apps/nextcloud.nix
+++ b/nixos/modules/services/web-apps/nextcloud.nix
@@ -86,7 +86,7 @@ in {
     package = mkOption {
       type = types.package;
       description = "Which package to use for the Nextcloud instance.";
-      relatedPackages = [ "nextcloud18" "nextcloud19" "nextcloud20" ];
+      relatedPackages = [ "nextcloud19" "nextcloud20" "nextcloud21" ];
     };
 
     maxUploadSize = mkOption {
@@ -348,7 +348,7 @@ in {
       ];
 
       warnings = let
-        latest = 20;
+        latest = 21;
         upgradeWarning = major: nixos:
           ''
             A legacy Nextcloud install (from before NixOS ${nixos}) may be installed.
@@ -366,9 +366,9 @@ in {
           Using config.services.nextcloud.poolConfig is deprecated and will become unsupported in a future release.
           Please migrate your configuration to config.services.nextcloud.poolSettings.
         '')
-        ++ (optional (versionOlder cfg.package.version "18") (upgradeWarning 17 "20.03"))
         ++ (optional (versionOlder cfg.package.version "19") (upgradeWarning 18 "20.09"))
-        ++ (optional (versionOlder cfg.package.version "20") (upgradeWarning 19 "21.05"));
+        ++ (optional (versionOlder cfg.package.version "20") (upgradeWarning 19 "21.05"))
+        ++ (optional (versionOlder cfg.package.version "21") (upgradeWarning 20 "21.05"));
 
       services.nextcloud.package = with pkgs;
         mkDefault (
@@ -378,14 +378,13 @@ in {
               nextcloud defined in an overlay, please set `services.nextcloud.package` to
               `pkgs.nextcloud`.
             ''
-          else if versionOlder stateVersion "20.03" then nextcloud17
           else if versionOlder stateVersion "20.09" then nextcloud18
           # 21.03 will not be an official release - it was instead 21.05.
           # This versionOlder statement remains set to 21.03 for backwards compatibility.
           # See https://github.com/NixOS/nixpkgs/pull/108899 and
           # https://github.com/NixOS/rfcs/blob/master/rfcs/0080-nixos-release-schedule.md.
           else if versionOlder stateVersion "21.03" then nextcloud19
-          else nextcloud20
+          else nextcloud21
         );
     }
 
diff --git a/nixos/modules/services/web-apps/nextcloud.xml b/nixos/modules/services/web-apps/nextcloud.xml
index 6cbfda118c4..83a6f68edcb 100644
--- a/nixos/modules/services/web-apps/nextcloud.xml
+++ b/nixos/modules/services/web-apps/nextcloud.xml
@@ -11,7 +11,7 @@
   desktop client is packaged at <literal>pkgs.nextcloud-client</literal>.
  </para>
  <para>
-  The current default by NixOS is <package>nextcloud20</package> which is also the latest
+  The current default by NixOS is <package>nextcloud21</package> which is also the latest
   major version available.
  </para>
  <section xml:id="module-services-nextcloud-basic-usage">
diff --git a/pkgs/servers/nextcloud/default.nix b/pkgs/servers/nextcloud/default.nix
index a40dd71fafd..53625941b61 100644
--- a/pkgs/servers/nextcloud/default.nix
+++ b/pkgs/servers/nextcloud/default.nix
@@ -31,24 +31,19 @@ let
     };
   };
 in {
-  nextcloud17 = throw ''
-    Nextcloud v17 has been removed from `nixpkgs` as the support for it will be dropped
-    by upstream within the lifetime of NixOS 20.09[1]. Please upgrade to Nextcloud v18 by
+  nextcloud18 = throw ''
+    Nextcloud v18 has been removed from `nixpkgs` as the support for it was dropped
+    by upstream in 2021-01. Please upgrade to at least Nextcloud v19 by
     declaring
 
-        services.nextcloud.package = pkgs.nextcloud18;
+        services.nextcloud.package = pkgs.nextcloud19;
 
     in your NixOS config.
 
     [1] https://docs.nextcloud.com/server/18/admin_manual/release_schedule.html
   '';
 
-  nextcloud18 = generic {
-    version = "18.0.10";
-    sha256 = "0kv9mdn36shr98kh27969b8xs7pgczbyjklrfskxy9mph7bbzir6";
-    eol = true;
-  };
-
+  # FIXME(@Ma27) remove on 2021-06
   nextcloud19 = generic {
     version = "19.0.6";
     sha256 = "sha256-pqqIayE0OyTailtd2zeYi+G1APjv/YHqyO8jCpq7KJg=";
@@ -61,4 +56,9 @@ in {
     version = "20.0.7";
     sha256 = "sha256-jO2Ct3K/CvZ9W+EyPkD5d0KbwKK8yGQJXvx4dnUAtys=";
   };
+
+  nextcloud21 = generic {
+    version = "21.0.0";
+    sha256 = "sha256-zq2u72doWhGvxbI7Coa6PHvQp7E41dHswFJiODZV8fA=";
+  };
 }
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 8403e1a925b..adcac4d6a44 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -6544,7 +6544,7 @@ in
   grocy = callPackage ../servers/grocy { };
 
   inherit (callPackage ../servers/nextcloud {})
-    nextcloud17 nextcloud18 nextcloud19 nextcloud20;
+    nextcloud18 nextcloud19 nextcloud20 nextcloud21;
 
   nextcloud-client = libsForQt5.callPackage ../applications/networking/nextcloud-client { };