diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 31c821728e..0f1e6d9138 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -6,7 +6,6 @@ on:
 env:
   HOMEBREW_DEVELOPER: 1
   HOMEBREW_NO_AUTO_UPDATE: 1
-  HOMEBREW_BIG_SUR_TESTING: 1 # TODO: remove when Big Sur is released.
 jobs:
   tests:
     if: github.repository == 'Homebrew/brew'
diff --git a/Library/Homebrew/dev-cmd/tests.rb b/Library/Homebrew/dev-cmd/tests.rb
index 8278514e96..a6f54d9d60 100644
--- a/Library/Homebrew/dev-cmd/tests.rb
+++ b/Library/Homebrew/dev-cmd/tests.rb
@@ -64,7 +64,6 @@ module Homebrew
       ENV["HOMEBREW_TEST_GENERIC_OS"] = "1" if args.generic?
       ENV["HOMEBREW_TEST_ONLINE"] = "1" if args.online?
       ENV["HOMEBREW_SORBET_RUNTIME"] = "1"
-      ENV["HOMEBREW_BIG_SUR_TESTING"] = "1"
 
       ENV["USER"] ||= system_command!("id", args: ["-nu"]).stdout.chomp
 
diff --git a/Library/Homebrew/extend/os/mac/diagnostic.rb b/Library/Homebrew/extend/os/mac/diagnostic.rb
index 65ed503480..9f51d5ec92 100644
--- a/Library/Homebrew/extend/os/mac/diagnostic.rb
+++ b/Library/Homebrew/extend/os/mac/diagnostic.rb
@@ -107,12 +107,7 @@ module Homebrew
         return if Homebrew::EnvConfig.developer?
 
         who = +"We"
-        # TODO: remove when Big Sur is supported.
-        what = if MacOS.version == :big_sur
-          return if ENV["HOMEBREW_BIG_SUR_TESTING"]
-
-          "released but not yet supported version"
-        elsif OS::Mac.prerelease?
+        what = if OS::Mac.prerelease?
           "pre-release version"
         elsif OS::Mac.outdated_release?
           who << " (and Apple)"