diff --git a/nixos/tests/all-tests.nix b/nixos/tests/all-tests.nix
index 7b506eb5f87c..b2810ceacf56 100644
--- a/nixos/tests/all-tests.nix
+++ b/nixos/tests/all-tests.nix
@@ -323,6 +323,7 @@ in {
   firefox-devedition = handleTest ./firefox.nix { firefoxPackage = pkgs.firefox-devedition; };
   firefox-esr    = handleTest ./firefox.nix { firefoxPackage = pkgs.firefox-esr; }; # used in `tested` job
   firefox-esr-115 = handleTest ./firefox.nix { firefoxPackage = pkgs.firefox-esr-115; };
+  firefox-esr-128 = handleTest ./firefox.nix { firefoxPackage = pkgs.firefox-esr-128; };
   firefoxpwa = handleTest ./firefoxpwa.nix {};
   firejail = handleTest ./firejail.nix {};
   firewall = handleTest ./firewall.nix { nftables = false; };
diff --git a/pkgs/applications/networking/browsers/firefox/packages.nix b/pkgs/applications/networking/browsers/firefox/packages.nix
index a16b7e659595..cd8c2b00fda4 100644
--- a/pkgs/applications/networking/browsers/firefox/packages.nix
+++ b/pkgs/applications/networking/browsers/firefox/packages.nix
@@ -94,6 +94,35 @@
     };
   };
 
+  firefox-esr-128 = buildMozillaMach rec {
+    pname = "firefox";
+    version = "128.0esr";
+    src = fetchurl {
+      url = "mirror://mozilla/firefox/releases/${version}/source/firefox-${version}.source.tar.xz";
+      sha512 = "b65f28a530016fd0cf46bc5f55fdec2a0cc66bd9a71b606b8d6dace1f6ce1d8744b08298549cf9c338eca1d9331dd506874ed3244bd3b856c153bd765e6071be";
+    };
+
+    meta = {
+      changelog = "https://www.mozilla.org/en-US/firefox/${version}/releasenotes/";
+      description = "Web browser built from Firefox source tree";
+      homepage = "http://www.mozilla.com/en-US/firefox/";
+      maintainers = with lib.maintainers; [ hexa ];
+      platforms = lib.platforms.unix;
+      badPlatforms = lib.platforms.darwin;
+      broken = stdenv.buildPlatform.is32bit; # since Firefox 60, build on 32-bit platforms fails with "out of memory".
+                                             # not in `badPlatforms` because cross-compilation on 64-bit machine might work.
+      maxSilent = 14400; # 4h, double the default of 7200s (c.f. #129212, #129115)
+      license = lib.licenses.mpl20;
+      mainProgram = "firefox";
+    };
+    tests = [ nixosTests.firefox ];
+    updateScript = callPackage ./update.nix {
+      attrPath = "firefox-esr-128-unwrapped";
+      versionPrefix = "128";
+      versionSuffix = "esr";
+    };
+  };
+
   firefox-esr-115 = (buildMozillaMach rec {
     pname = "firefox-esr-115";
     version = "115.13.0esr";
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 7f72f3fa8987..29c1b8474eaa 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -30770,6 +30770,7 @@ with pkgs;
   firefox-beta-unwrapped = firefoxPackages.firefox-beta;
   firefox-devedition-unwrapped = firefoxPackages.firefox-devedition;
   firefox-esr-115-unwrapped = firefoxPackages.firefox-esr-115;
+  firefox-esr-128-unwrapped = firefoxPackages.firefox-esr-128;
   firefox-esr-unwrapped = firefoxPackages.firefox-esr-115;
 
   firefox = wrapFirefox firefox-unwrapped { };
@@ -30788,13 +30789,19 @@ with pkgs;
 
   firefox-mobile = callPackage ../applications/networking/browsers/firefox/mobile-config.nix { };
 
-  firefox-esr = firefox-esr-115;
+  firefox-esr-128 = wrapFirefox firefox-esr-128-unwrapped {
+    nameSuffix = "-esr";
+    desktopName = "Firefox ESR";
+    wmClass = "firefox-esr";
+    icon = "firefox-esr";
+  };
   firefox-esr-115 = wrapFirefox firefox-esr-115-unwrapped {
     nameSuffix = "-esr";
     desktopName = "Firefox ESR";
     wmClass = "firefox-esr";
     icon = "firefox-esr";
   };
+  firefox-esr = firefox-esr-115;
 
   firefox-bin-unwrapped = callPackage ../applications/networking/browsers/firefox-bin {
     channel = "release";