diff --git a/doc/release-notes/rl-2605.section.md b/doc/release-notes/rl-2605.section.md
index 1c2b74db69fc..26a7a66c767c 100644
--- a/doc/release-notes/rl-2605.section.md
+++ b/doc/release-notes/rl-2605.section.md
@@ -3,7 +3,8 @@
 ## Highlights {#sec-nixpkgs-release-26.05-highlights}
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
 
-- Create the first release note entry in this section!
+- GCC has been updated from GCC 14 to GCC 15.
+  This introduces some backwards incompatible changes; Refer to the [upstream porting guide](https://gcc.gnu.org/gcc-15/porting_to.html) for details.
 
 ## Backward Incompatibilities {#sec-nixpkgs-release-26.05-incompatibilities}
 
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 330b70bdb4a5..79a0cdde7aa9 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -4410,7 +4410,7 @@ with pkgs;
   gerbilPackages-unstable = pkgs.gerbil-support.gerbilPackages-unstable; # NB: don't recurseIntoAttrs for (unstable!) libraries
   glow-lang = pkgs.gerbilPackages-unstable.glow-lang;
 
-  default-gcc-version = 14;
+  default-gcc-version = 15;
   gcc = pkgs.${"gcc${toString default-gcc-version}"};
   gccFun = callPackage ../development/compilers/gcc;
   gcc-unwrapped = gcc.cc;