diff --git a/Library/Homebrew/dev-cmd/livecheck.rb b/Library/Homebrew/dev-cmd/livecheck.rb
index 0fe8660221..d6a2930a08 100644
--- a/Library/Homebrew/dev-cmd/livecheck.rb
+++ b/Library/Homebrew/dev-cmd/livecheck.rb
@@ -9,8 +9,6 @@ require "livecheck/strategy"
 module Homebrew
   module_function
 
-  WATCHLIST_PATH = File.expand_path(Homebrew::EnvConfig.livecheck_watchlist).freeze
-
   sig { returns(CLI::Parser) }
   def livecheck_args
     Homebrew::CLI::Parser.new do
@@ -19,7 +17,7 @@ module Homebrew
 
         If no formula or cask argument is passed, the list of formulae and
         casks to check is taken from `HOMEBREW_LIVECHECK_WATCHLIST` or
-        `~/.brew_livecheck_watchlist`.
+        `~/.homebrew/livecheck_watchlist.txt`.
       EOS
       switch "--full-name",
              description: "Print formulae and casks with fully-qualified names."
@@ -50,6 +48,22 @@ module Homebrew
     end
   end
 
+  def watchlist_path
+    @watchlist_path ||= begin
+      watchlist = File.expand_path(Homebrew::EnvConfig.livecheck_watchlist)
+
+      unless File.exist?(watchlist)
+        previous_default_watchlist = File.expand_path("~/.brew_livecheck_watchlist")
+        if File.exist?(previous_default_watchlist)
+          odeprecated "~/.brew_livecheck_watchlist", "~/.homebrew/livecheck_watchlist.txt"
+          watchlist = previous_default_watchlist
+        end
+      end
+
+      watchlist
+    end
+  end
+
   def livecheck
     args = livecheck_args.parse
 
@@ -82,9 +96,9 @@ module Homebrew
         else
           args.named.to_formulae_and_casks
         end
-      elsif File.exist?(WATCHLIST_PATH)
+      elsif File.exist?(watchlist_path)
         begin
-          names = Pathname.new(WATCHLIST_PATH).read.lines
+          names = Pathname.new(watchlist_path).read.lines
                           .reject { |line| line.start_with?("#") || line.blank? }
                           .map(&:strip)
 
diff --git a/Library/Homebrew/env_config.rb b/Library/Homebrew/env_config.rb
index a648f0ef05..13fa4d8bbf 100644
--- a/Library/Homebrew/env_config.rb
+++ b/Library/Homebrew/env_config.rb
@@ -241,8 +241,9 @@ module Homebrew
       HOMEBREW_LIVECHECK_WATCHLIST:              {
         description:  "Consult this file for the list of formulae to check by default when no formula argument " \
                       "is passed to `brew livecheck`.",
-        default_text: "`$HOME/.brew_livecheck_watchlist`",
-        default:      "~/.brew_livecheck_watchlist",
+        default_text: "`$XDG_CONFIG_HOME/homebrew/livecheck_watchlist.txt` if `$XDG_CONFIG_HOME` is set " \
+                      "or `$HOME/.homebrew/livecheck_watchlist.txt` otherwise.",
+        default:      "#{ENV.fetch("HOMEBREW_USER_CONFIG_HOME")}/livecheck_watchlist.txt",
       },
       HOMEBREW_LOGS:                             {
         description:  "Use this directory to store log files.",
@@ -362,6 +363,11 @@ module Homebrew
         description:  "Use this as the `svn`(1) binary.",
         default_text: "A Homebrew-built Subversion (if installed), or the system-provided binary.",
       },
+      HOMEBREW_SYSTEM_ENV_TAKES_PRIORITY:        {
+        description: "If set in Homebrew's system-wide environment file (`/etc/homebrew/brew.env`), " \
+                     "the system-wide environment file will be loaded last to override any prefix or user settings.",
+        boolean:     true,
+      },
       HOMEBREW_TEMP:                             {
         description:  "Use this path as the temporary directory for building packages. Changing " \
                       "this may be needed if your system temporary directory and Homebrew prefix are on " \
diff --git a/Library/Homebrew/manpages/brew.1.md.erb b/Library/Homebrew/manpages/brew.1.md.erb
index 79c54d0e77..ab3cabebe3 100644
--- a/Library/Homebrew/manpages/brew.1.md.erb
+++ b/Library/Homebrew/manpages/brew.1.md.erb
@@ -144,6 +144,20 @@ Note that environment variables must have a value set to be detected. For
 example, run `export HOMEBREW_NO_INSECURE_REDIRECT=1` rather than just
 `export HOMEBREW_NO_INSECURE_REDIRECT`.
 
+`HOMEBREW_*` environment variables can also be set in Homebrew's environment
+files:
+
+* `/etc/homebrew/brew.env` (system-wide)
+
+* `$HOMEBREW_PREFIX/etc/homebrew/brew.env` (prefix-specific)
+
+* `$XDG_CONFIG_HOME/homebrew/brew.env` if `$XDG_CONFIG_HOME` is set or
+  `$HOME/.homebrew/brew.env` otherwise (user-specific)
+
+User-specific environment files take precedence over prefix-specific files and
+prefix-specific files take precedence over system-wide files (unless
+`HOMEBREW_SYSTEM_ENV_TAKES_PRIORITY` is set, see below).
+
 <%= environment_variables %>
 
 ## USING HOMEBREW BEHIND A PROXY
diff --git a/bin/brew b/bin/brew
index afc02e9eb8..60d67b29d8 100755
--- a/bin/brew
+++ b/bin/brew
@@ -68,12 +68,61 @@ then
   then
     HOMEBREW_PREFIX="/usr/local"
   fi
+  unset USR_LOCAL_BREW_FILE_DIRECTORY USR_LOCAL_HOMEBREW_REPOSITORY
 fi
 
+unset BREW_FILE_DIRECTORY
+
 # If the location of HOMEBREW_LIBRARY changes
 # keg_relocate.rb, formula_cellar_checks.rb, and test/global_spec.rb need to change.
 HOMEBREW_LIBRARY="${HOMEBREW_REPOSITORY}/Library"
 
+# Load Homebrew's variable configuration files from disk.
+# First, load the system-wide configuration.
+if [[ -f "/etc/homebrew/brew.env" ]]
+then
+  unset SYSTEM_ENV_TAKES_PRIORITY
+  # only load HOMEBREW_*=* lines
+  SYSTEM_HOMEBREW_ENV="$(grep -E '^HOMEBREW_[A-Z_]+=.*$' "/etc/homebrew/brew.env")"
+  if [[ -n "${HOMEBREW_SYSTEM_ENV_TAKES_PRIORITY-}" ]]
+  then
+    SYSTEM_ENV_TAKES_PRIORITY="1"
+  else
+    eval "${SYSTEM_HOMEBREW_ENV}"
+  fi
+fi
+
+# Next, load the prefix configuration
+if [[ -f "${HOMEBREW_PREFIX}/etc/homebrew/brew.env" ]]
+then
+  # only load HOMEBREW_*=* lines
+  PREFIX_HOMEBREW_ENV="$(grep -E '^HOMEBREW_[A-Z_]+=.*$' "${HOMEBREW_PREFIX}/etc/homebrew/brew.env")"
+  eval "${PREFIX_HOMEBREW_ENV}"
+  unset PREFIX_HOMEBREW_ENV
+fi
+
+# Finally, load the user configuration
+if [[ -n "${XDG_CONFIG_HOME-}" ]]
+then
+  HOMEBREW_USER_CONFIG_HOME="${XDG_CONFIG_HOME}/homebrew"
+else
+  HOMEBREW_USER_CONFIG_HOME="${HOME}/.homebrew"
+fi
+if [[ -f "${HOMEBREW_USER_CONFIG_HOME}/brew.env" ]]
+then
+  # only load HOMEBREW_*=* lines
+  USER_HOMEBREW_ENV="$(grep -E '^HOMEBREW_[A-Z_]+=.*$' "${HOMEBREW_USER_CONFIG_HOME}/brew.env")"
+  eval "${USER_HOMEBREW_ENV}"
+  unset USER_HOMEBREW_ENV
+fi
+
+# If the system configuration takes priority, load it last.
+if [[ -n "${SYSTEM_ENV_TAKES_PRIORITY-}" ]]
+then
+  eval "${SYSTEM_HOMEBREW_ENV}"
+fi
+unset SYSTEM_HOMEBREW_ENV
+
 # Copy and export all HOMEBREW_* variables previously mentioned in
 # manpage or used elsewhere by Homebrew.
 
@@ -121,6 +170,7 @@ export HOMEBREW_BREW_FILE
 export HOMEBREW_PREFIX
 export HOMEBREW_REPOSITORY
 export HOMEBREW_LIBRARY
+export HOMEBREW_USER_CONFIG_HOME
 
 # set from user environment
 # shellcheck disable=SC2154
diff --git a/docs/Manpage.md b/docs/Manpage.md
index 7b8cb102a3..c748adcc89 100644
--- a/docs/Manpage.md
+++ b/docs/Manpage.md
@@ -1332,7 +1332,7 @@ Check for newer versions of formulae and/or casks from upstream.
 
 If no formula or cask argument is passed, the list of formulae and
 casks to check is taken from `HOMEBREW_LIVECHECK_WATCHLIST` or
-`~/.brew_livecheck_watchlist`.
+`~/.homebrew/livecheck_watchlist.txt`.
 
 * `--full-name`:
   Print formulae and casks with fully-qualified names.
@@ -2059,6 +2059,20 @@ Note that environment variables must have a value set to be detected. For
 example, run `export HOMEBREW_NO_INSECURE_REDIRECT=1` rather than just
 `export HOMEBREW_NO_INSECURE_REDIRECT`.
 
+`HOMEBREW_*` environment variables can also be set in Homebrew's environment
+files:
+
+* `/etc/homebrew/brew.env` (system-wide)
+
+* `$HOMEBREW_PREFIX/etc/homebrew/brew.env` (prefix-specific)
+
+* `$XDG_CONFIG_HOME/homebrew/brew.env` if `$XDG_CONFIG_HOME` is set or
+  `$HOME/.homebrew/brew.env` otherwise (user-specific)
+
+User-specific environment files take precedence over prefix-specific files and
+prefix-specific files take precedence over system-wide files (unless
+`HOMEBREW_SYSTEM_ENV_TAKES_PRIORITY` is set, see below).
+
 - `HOMEBREW_API_DOMAIN`
   <br>Use this URL as the download mirror for Homebrew JSON API. If metadata files at that URL are temporarily unavailable, the default API domain will be used as a fallback mirror.
 
@@ -2243,7 +2257,7 @@ example, run `export HOMEBREW_NO_INSECURE_REDIRECT=1` rather than just
 - `HOMEBREW_LIVECHECK_WATCHLIST`
   <br>Consult this file for the list of formulae to check by default when no formula argument is passed to `brew livecheck`.
 
-  *Default:* `$HOME/.brew_livecheck_watchlist`
+  *Default:* `$XDG_CONFIG_HOME/homebrew/livecheck_watchlist.txt` if `$XDG_CONFIG_HOME` is set or `$HOME/.homebrew/livecheck_watchlist.txt` otherwise.
 
 - `HOMEBREW_LOGS`
   <br>Use this directory to store log files.
@@ -2328,6 +2342,9 @@ example, run `export HOMEBREW_NO_INSECURE_REDIRECT=1` rather than just
 
   *Default:* A Homebrew-built Subversion (if installed), or the system-provided binary.
 
+- `HOMEBREW_SYSTEM_ENV_TAKES_PRIORITY`
+  <br>If set in Homebrew's system-wide environment file (`/etc/homebrew/brew.env`), the system-wide environment file will be loaded last to override any prefix or user settings.
+
 - `HOMEBREW_TEMP`
   <br>Use this path as the temporary directory for building packages. Changing this may be needed if your system temporary directory and Homebrew prefix are on different volumes, as macOS has trouble moving symlinks across volumes when the target does not yet exist. This issue typically occurs when using FileVault or custom SSD configurations.
 
diff --git a/manpages/brew.1 b/manpages/brew.1
index 9225cd3697..455111fbff 100644
--- a/manpages/brew.1
+++ b/manpages/brew.1
@@ -1900,7 +1900,7 @@ Print the cached linkage values stored in \fBHOMEBREW_CACHE\fR, set by a previou
 Check for newer versions of formulae and/or casks from upstream\.
 .
 .P
-If no formula or cask argument is passed, the list of formulae and casks to check is taken from \fBHOMEBREW_LIVECHECK_WATCHLIST\fR or \fB~/\.brew_livecheck_watchlist\fR\.
+If no formula or cask argument is passed, the list of formulae and casks to check is taken from \fBHOMEBREW_LIVECHECK_WATCHLIST\fR or \fB~/\.homebrew/livecheck_watchlist\.txt\fR\.
 .
 .TP
 \fB\-\-full\-name\fR
@@ -2935,6 +2935,23 @@ Many Homebrew Cask commands accept one or more \fIcask\fR arguments\. These can
 .SH "ENVIRONMENT"
 Note that environment variables must have a value set to be detected\. For example, run \fBexport HOMEBREW_NO_INSECURE_REDIRECT=1\fR rather than just \fBexport HOMEBREW_NO_INSECURE_REDIRECT\fR\.
 .
+.P
+\fBHOMEBREW_*\fR environment variables can also be set in Homebrew\'s environment files:
+.
+.IP "\(bu" 4
+\fB/etc/homebrew/brew\.env\fR (system\-wide)
+.
+.IP "\(bu" 4
+\fB$HOMEBREW_PREFIX/etc/homebrew/brew\.env\fR (prefix\-specific)
+.
+.IP "\(bu" 4
+\fB$XDG_CONFIG_HOME/homebrew/brew\.env\fR if \fB$XDG_CONFIG_HOME\fR is set or \fB$HOME/\.homebrew/brew\.env\fR otherwise (user\-specific)
+.
+.IP "" 0
+.
+.P
+User\-specific environment files take precedence over prefix\-specific files and prefix\-specific files take precedence over system\-wide files (unless \fBHOMEBREW_SYSTEM_ENV_TAKES_PRIORITY\fR is set, see below)\.
+.
 .TP
 \fBHOMEBREW_API_DOMAIN\fR
 .
@@ -3281,7 +3298,7 @@ Print this text before the installation summary of each successful build\.
 Consult this file for the list of formulae to check by default when no formula argument is passed to \fBbrew livecheck\fR\.
 .
 .IP
-\fIDefault:\fR \fB$HOME/\.brew_livecheck_watchlist\fR
+\fIDefault:\fR \fB$XDG_CONFIG_HOME/homebrew/livecheck_watchlist\.txt\fR if \fB$XDG_CONFIG_HOME\fR is set or \fB$HOME/\.homebrew/livecheck_watchlist\.txt\fR otherwise\.
 .
 .TP
 \fBHOMEBREW_LOGS\fR
@@ -3443,6 +3460,12 @@ Use this as the \fBsvn\fR(1) binary\.
 \fIDefault:\fR A Homebrew\-built Subversion (if installed), or the system\-provided binary\.
 .
 .TP
+\fBHOMEBREW_SYSTEM_ENV_TAKES_PRIORITY\fR
+.
+.br
+If set in Homebrew\'s system\-wide environment file (\fB/etc/homebrew/brew\.env\fR), the system\-wide environment file will be loaded last to override any prefix or user settings\.
+.
+.TP
 \fBHOMEBREW_TEMP\fR
 .
 .br