diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 2795d19d3d..ffd47c945f 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -255,9 +255,6 @@ jobs:
           - name: tests (online)
             test-flags: --online --coverage
             runs-on: ubuntu-22.04
-          - name: tests (no-compatibility mode)
-            test-flags: --no-compat --coverage
-            runs-on: ubuntu-22.04
           - name: tests (generic OS)
             test-flags: --generic --coverage
             runs-on: ubuntu-22.04
diff --git a/Library/Homebrew/.simplecov b/Library/Homebrew/.simplecov
index 039fc2195b..e2bada638c 100755
--- a/Library/Homebrew/.simplecov
+++ b/Library/Homebrew/.simplecov
@@ -63,7 +63,6 @@ SimpleCov.start do
   add_filter %r{^/constants.rb$}
   add_filter %r{^/postinstall.rb$}
   add_filter %r{^/test.rb$}
-  add_filter %r{^/compat/}
   add_filter %r{^/dev-cmd/tests.rb$}
   add_filter %r{^/test/}
   add_filter %r{^/vendor/}
diff --git a/Library/Homebrew/.yardopts b/Library/Homebrew/.yardopts
index b86f778054..ef2b4836c7 100644
--- a/Library/Homebrew/.yardopts
+++ b/Library/Homebrew/.yardopts
@@ -6,7 +6,6 @@
 --template-path yard/templates
 --exclude test/
 --exclude vendor/
---exclude compat/
 extend/os/**/*.rb
 **/*.rb
 -
diff --git a/Library/Homebrew/compat/cask.rb b/Library/Homebrew/compat/cask.rb
deleted file mode 100644
index 8c5121759a..0000000000
--- a/Library/Homebrew/compat/cask.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-# typed: true
-# frozen_string_literal: true
diff --git a/Library/Homebrew/compat/early.rb b/Library/Homebrew/compat/early.rb
deleted file mode 100644
index b4806eee61..0000000000
--- a/Library/Homebrew/compat/early.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-# typed: strict
-# frozen_string_literal: true
diff --git a/Library/Homebrew/compat/formula.rb b/Library/Homebrew/compat/formula.rb
deleted file mode 100644
index 8c5121759a..0000000000
--- a/Library/Homebrew/compat/formula.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-# typed: true
-# frozen_string_literal: true
diff --git a/Library/Homebrew/compat/late.rb b/Library/Homebrew/compat/late.rb
deleted file mode 100644
index 6e36cebe11..0000000000
--- a/Library/Homebrew/compat/late.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-# typed: strict
-# frozen_string_literal: true
-
-require "compat/formula"
-require "compat/cask"
diff --git a/Library/Homebrew/dev-cmd/tests.rb b/Library/Homebrew/dev-cmd/tests.rb
index e49b62cf6d..af59988836 100644
--- a/Library/Homebrew/dev-cmd/tests.rb
+++ b/Library/Homebrew/dev-cmd/tests.rb
@@ -19,8 +19,6 @@ module Homebrew
              description: "Generate code coverage reports."
       switch "--generic",
              description: "Run only OS-agnostic tests."
-      switch "--no-compat",
-             description: "Do not load the compatibility layer when running tests."
       switch "--online",
              description: "Include tests that use the GitHub API and tests that use any of the taps for " \
                           "official external commands."
@@ -125,7 +123,6 @@ module Homebrew
       end
 
       parallel_rspec_log_name = "parallel_runtime_rspec"
-      parallel_rspec_log_name = "#{parallel_rspec_log_name}.no_compat" if args.no_compat?
       parallel_rspec_log_name = "#{parallel_rspec_log_name}.generic" if args.generic?
       parallel_rspec_log_name = "#{parallel_rspec_log_name}.online" if args.online?
       parallel_rspec_log_name = "#{parallel_rspec_log_name}.log"
@@ -230,7 +227,6 @@ module Homebrew
     ENV["HOMEBREW_TESTS"] = "1"
     ENV["HOMEBREW_NO_AUTO_UPDATE"] = "1"
     ENV["HOMEBREW_NO_ANALYTICS_THIS_RUN"] = "1"
-    ENV["HOMEBREW_NO_COMPAT"] = "1" if args.no_compat?
     ENV["HOMEBREW_TEST_GENERIC_OS"] = "1" if args.generic?
     ENV["HOMEBREW_TEST_ONLINE"] = "1" if args.online?
     ENV["HOMEBREW_SORBET_RUNTIME"] = "1"
diff --git a/Library/Homebrew/env_config.rb b/Library/Homebrew/env_config.rb
index 375bc1e92d..a4ec38c4e8 100644
--- a/Library/Homebrew/env_config.rb
+++ b/Library/Homebrew/env_config.rb
@@ -288,10 +288,6 @@ module Homebrew
         default_text: "`$NO_COLOR`.",
         boolean:      true,
       },
-      HOMEBREW_NO_COMPAT:                        {
-        description: "If set, disable all use of legacy compatibility code.",
-        boolean:     true,
-      },
       HOMEBREW_NO_EMOJI:                         {
         description: "If set, do not print `HOMEBREW_INSTALL_BADGE` on a successful build.",
         boolean:     true,
diff --git a/Library/Homebrew/env_config.rbi b/Library/Homebrew/env_config.rbi
index 3f664cd315..bf67f9c624 100644
--- a/Library/Homebrew/env_config.rbi
+++ b/Library/Homebrew/env_config.rbi
@@ -169,9 +169,6 @@ module Homebrew::EnvConfig
   sig { returns(T::Boolean) }
   def self.no_color?; end
 
-  sig { returns(T::Boolean) }
-  def self.no_compat?; end
-
   sig { returns(T::Boolean) }
   def self.no_emoji?; end
 
diff --git a/Library/Homebrew/extend/kernel.rb b/Library/Homebrew/extend/kernel.rb
index 635eb9530d..77c7547376 100644
--- a/Library/Homebrew/extend/kernel.rb
+++ b/Library/Homebrew/extend/kernel.rb
@@ -112,7 +112,6 @@ module Kernel
 
     # Try to show the most relevant location in message, i.e. (if applicable):
     # - Location in a formula.
-    # - Location outside of 'compat/'.
     # - Location of caller of deprecated method (if all else fails).
     backtrace = caller
 
diff --git a/Library/Homebrew/global.rb b/Library/Homebrew/global.rb
index 1f87b4c3a9..de6e01e5e4 100644
--- a/Library/Homebrew/global.rb
+++ b/Library/Homebrew/global.rb
@@ -70,7 +70,6 @@ HOMEBREW_PULL_OR_COMMIT_URL_REGEX =
 HOMEBREW_BOTTLES_EXTNAME_REGEX = /\.([a-z0-9_]+)\.bottle\.(?:(\d+)\.)?tar\.gz$/.freeze
 
 require "env_config"
-require "compat/early" unless Homebrew::EnvConfig.no_compat?
 require "macos_versions"
 require "os"
 require "messages"
@@ -151,5 +150,3 @@ require "utils"
 require "official_taps"
 require "tap"
 require "tap_constants"
-
-require "compat/late" unless Homebrew::EnvConfig.no_compat?
diff --git a/Library/Homebrew/rubocops/extend/formula_cop.rb b/Library/Homebrew/rubocops/extend/formula_cop.rb
index 889924c267..38b0b0725d 100644
--- a/Library/Homebrew/rubocops/extend/formula_cop.rb
+++ b/Library/Homebrew/rubocops/extend/formula_cop.rb
@@ -206,8 +206,7 @@ module RuboCop
       end
 
       def file_path_allowed?
-        paths_to_exclude = [%r{/Library/Homebrew/compat/},
-                            %r{/Library/Homebrew/test/}]
+        paths_to_exclude = [%r{/Library/Homebrew/test/}]
         return true if @file_path.nil? # file_path is nil when source is directly passed to the cop, e.g. in specs
 
         @file_path !~ Regexp.union(paths_to_exclude)
diff --git a/Library/Homebrew/test/spec_helper.rb b/Library/Homebrew/test/spec_helper.rb
index 1ea10a0493..408e370d7b 100644
--- a/Library/Homebrew/test/spec_helper.rb
+++ b/Library/Homebrew/test/spec_helper.rb
@@ -118,10 +118,6 @@ RSpec.configure do |config|
   config.include(Test::Helper::MkTmpDir)
   config.include(Test::Helper::OutputAsTTY)
 
-  config.before(:each, :needs_compat) do
-    skip "Requires the compatibility layer." if ENV["HOMEBREW_NO_COMPAT"]
-  end
-
   config.before(:each, :needs_linux) do
     skip "Not running on Linux." unless OS.linux?
   end
diff --git a/completions/bash/brew b/completions/bash/brew
index 9ba541ce01..001b443f7b 100644
--- a/completions/bash/brew
+++ b/completions/bash/brew
@@ -2090,7 +2090,6 @@ _brew_tests() {
       --debug
       --generic
       --help
-      --no-compat
       --online
       --only
       --quiet
diff --git a/completions/fish/brew.fish b/completions/fish/brew.fish
index 9d88c13fab..84691cd721 100644
--- a/completions/fish/brew.fish
+++ b/completions/fish/brew.fish
@@ -1415,7 +1415,6 @@ __fish_brew_complete_arg 'tests' -l coverage -d 'Generate code coverage reports'
 __fish_brew_complete_arg 'tests' -l debug -d 'Display any debugging information'
 __fish_brew_complete_arg 'tests' -l generic -d 'Run only OS-agnostic tests'
 __fish_brew_complete_arg 'tests' -l help -d 'Show this message'
-__fish_brew_complete_arg 'tests' -l no-compat -d 'Do not load the compatibility layer when running tests'
 __fish_brew_complete_arg 'tests' -l online -d 'Include tests that use the GitHub API and tests that use any of the taps for official external commands'
 __fish_brew_complete_arg 'tests' -l only -d 'Run only test_script`_spec.rb`. Appending `:`line_number will start at a specific line'
 __fish_brew_complete_arg 'tests' -l quiet -d 'Make some output more quiet'
diff --git a/completions/zsh/_brew b/completions/zsh/_brew
index 6e14cc5711..463753aa62 100644
--- a/completions/zsh/_brew
+++ b/completions/zsh/_brew
@@ -1728,7 +1728,6 @@ _brew_tests() {
     '--debug[Display any debugging information]' \
     '--generic[Run only OS-agnostic tests]' \
     '--help[Show this message]' \
-    '--no-compat[Do not load the compatibility layer when running tests]' \
     '--online[Include tests that use the GitHub API and tests that use any of the taps for official external commands]' \
     '(--changed)--only[Run only test_script`_spec.rb`. Appending `:`line_number will start at a specific line]' \
     '--quiet[Make some output more quiet]' \
diff --git a/docs/Homebrew-brew-Maintainer-Guide.md b/docs/Homebrew-brew-Maintainer-Guide.md
index f5162a094b..d0845a359d 100644
--- a/docs/Homebrew-brew-Maintainer-Guide.md
+++ b/docs/Homebrew-brew-Maintainer-Guide.md
@@ -46,7 +46,7 @@ There are many checks that run on every PR. The following is a quick list of the
 - `CI / tap syntax`: This runs `brew style` and `brew audit` on all official taps (note that although this runs on Linux, it does check all cask repos).
 - `CI / docker`: This builds and deploys a new Homebrew Docker image to GitHub Packages and Docker Hub.
 - `CI / test everything (macOS)`: This runs several checks on macOS including `brew tests`, `brew update-tests`, `brew test-bot --only-formulae --test-default-formula`, `brew readall` and `brew doctor`.
-- `CI / tests (no-compatibility mode)`, `CI / tests (generic OS)` and `CI / tests (Linux)`: These run `brew tests` with various options on Linux.
+- `CI / tests (generic OS)` and `CI / tests (Linux)`: These run `brew tests` with various options on Linux.
 - `Documentation CI / linting` and `rubydoc`: These check the prose and formatting of the written documentation, and verify the [rubydoc API documentation](https://rubydoc.brew.sh) can be built without issue.
 
 _Note that this list is non-exhaustive and can change over time._
diff --git a/docs/Manpage.md b/docs/Manpage.md
index 45fbf5ad7e..4faed0859f 100644
--- a/docs/Manpage.md
+++ b/docs/Manpage.md
@@ -1511,8 +1511,6 @@ Run Homebrew's unit and integration tests.
   Generate code coverage reports.
 * `--generic`:
   Run only OS-agnostic tests.
-* `--no-compat`:
-  Do not load the compatibility layer when running tests.
 * `--online`:
   Include tests that use the GitHub API and tests that use any of the taps for official external commands.
 * `--byebug`:
@@ -2204,9 +2202,6 @@ example, run `export HOMEBREW_NO_INSECURE_REDIRECT=1` rather than just
 
   *Default:* `$NO_COLOR`.
 
-- `HOMEBREW_NO_COMPAT`
-  <br>If set, disable all use of legacy compatibility code.
-
 - `HOMEBREW_NO_EMOJI`
   <br>If set, do not print `HOMEBREW_INSTALL_BADGE` on a successful build.
 
diff --git a/manpages/brew.1 b/manpages/brew.1
index 7bf8f0742e..9a7d2d37b3 100644
--- a/manpages/brew.1
+++ b/manpages/brew.1
@@ -2165,10 +2165,6 @@ Generate code coverage reports\.
 Run only OS\-agnostic tests\.
 .
 .TP
-\fB\-\-no\-compat\fR
-Do not load the compatibility layer when running tests\.
-.
-.TP
 \fB\-\-online\fR
 Include tests that use the GitHub API and tests that use any of the taps for official external commands\.
 .
@@ -3234,12 +3230,6 @@ If set, do not print text with colour added\.
 \fIDefault:\fR \fB$NO_COLOR\fR\.
 .
 .TP
-\fBHOMEBREW_NO_COMPAT\fR
-.
-.br
-If set, disable all use of legacy compatibility code\.
-.
-.TP
 \fBHOMEBREW_NO_EMOJI\fR
 .
 .br