diff --git a/nixos/tests/all-tests.nix b/nixos/tests/all-tests.nix
index cc473bba5c7..f7f57b3268e 100644
--- a/nixos/tests/all-tests.nix
+++ b/nixos/tests/all-tests.nix
@@ -267,6 +267,7 @@ 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-102 = handleTest ./firefox.nix { firefoxPackage = pkgs.firefox-esr-102; };
+  firefox-esr-115 = handleTest ./firefox.nix { firefoxPackage = pkgs.firefox-esr-115; };
   firejail = handleTest ./firejail.nix {};
   firewall = handleTest ./firewall.nix { nftables = false; };
   firewall-nftables = handleTest ./firewall.nix { nftables = true; };
diff --git a/pkgs/applications/networking/browsers/firefox/packages.nix b/pkgs/applications/networking/browsers/firefox/packages.nix
index ab41e7b224e..5a0f3ed4ddb 100644
--- a/pkgs/applications/networking/browsers/firefox/packages.nix
+++ b/pkgs/applications/networking/browsers/firefox/packages.nix
@@ -110,4 +110,32 @@
       versionSuffix = "esr";
     };
   };
+
+  firefox-esr-115 = buildMozillaMach rec {
+    pname = "firefox-esr-115";
+    version = "115.0esr";
+    applicationName = "Mozilla Firefox ESR";
+    src = fetchurl {
+      url = "mirror://mozilla/firefox/releases/${version}/source/firefox-${version}.source.tar.xz";
+      sha512 = "377ab48989ec17b64bd06fed8dd80dde50c06dd4120a6ca1c2fe90a20c85d1c0ef6143a73daeb0271fb20a04b0fb53d837e116b56c63718d517b07ed4243a3e9";
+    };
+
+    meta = {
+      changelog = "https://www.mozilla.org/en-US/firefox/${lib.removeSuffix "esr" version}/releasenotes/";
+      description = "A web browser built from Firefox Extended Support Release 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.
+      license = lib.licenses.mpl20;
+    };
+    tests = [ nixosTests.firefox-esr-115 ];
+    updateScript = callPackage ./update.nix {
+      attrPath = "firefox-esr-115-unwrapped";
+      versionPrefix = "115";
+      versionSuffix = "esr";
+    };
+  };
 }
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index cb773146d53..5ca30169b18 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -31203,6 +31203,7 @@ with pkgs;
   firefox-beta-unwrapped = firefoxPackages.firefox-beta;
   firefox-devedition-unwrapped = firefoxPackages.firefox-devedition;
   firefox-esr-102-unwrapped = firefoxPackages.firefox-esr-102;
+  firefox-esr-115-unwrapped = firefoxPackages.firefox-esr-115;
   firefox-esr-unwrapped = firefoxPackages.firefox-esr-102;
 
   firefox = wrapFirefox firefox-unwrapped { };
@@ -31213,6 +31214,7 @@ with pkgs;
 
   firefox-esr = firefox-esr-102;
   firefox-esr-102 = wrapFirefox firefox-esr-102-unwrapped { };
+  firefox-esr-115 = wrapFirefox firefox-esr-115-unwrapped { };
 
   firefox-bin-unwrapped = callPackage ../applications/networking/browsers/firefox-bin {
     inherit (gnome) adwaita-icon-theme;