diff --git a/doc/build-helpers/fetchers.chapter.md b/doc/build-helpers/fetchers.chapter.md
index 8ff1fdf11a19..bd606ea924f1 100644
--- a/doc/build-helpers/fetchers.chapter.md
+++ b/doc/build-helpers/fetchers.chapter.md
@@ -827,6 +827,10 @@ Additionally, the following optional arguments can be given:
 
   See [git sparse-checkout](https://git-scm.com/docs/git-sparse-checkout) for more information.
 
+*`rootDir`* (String)
+
+: When not empty, copy only contents of the subdirectory of the repository to the result. Automatically sets `sparseCheckout` and `nonConeMode` to avoid checking out any extra pieces. Incompatible with `leaveDotGit`.
+
 Some additional parameters for niche use-cases can be found listed in the function parameters in the declaration of `fetchgit`: `pkgs/build-support/fetchgit/default.nix`.
 Future parameters additions might also happen without immediately being documented here.
 
diff --git a/doc/release-notes/rl-2511.section.md b/doc/release-notes/rl-2511.section.md
index 2e54b34da408..023650e2664c 100644
--- a/doc/release-notes/rl-2511.section.md
+++ b/doc/release-notes/rl-2511.section.md
@@ -75,6 +75,7 @@
   * `$debug/lib/debug/.build-id/48/3bd7f7229bdb06462222e1e353e4f37e15c293.sourceoverlay` is a symlink to a directory with the same structure as the expanded `$sourceRoot` but containing only a copy of files which were patched during the build
   * `$debug/lib/debug/.build-id/48/3bd7f7229bdb06462222e1e353e4f37e15c293.debug` is the file containing debug symbols (like before).
 
+- `fetchgit`: Add `rootDir` argument to limit the resulting source to one subdirectory of the whole Git repository. Corresponding `--root-dir` option added to `nix-prefetch-git`.
 
 ## Nixpkgs Library {#sec-nixpkgs-release-25.11-lib}
 
diff --git a/pkgs/build-support/fetchgit/builder.sh b/pkgs/build-support/fetchgit/builder.sh
index 819b0127a852..393d0a57d163 100644
--- a/pkgs/build-support/fetchgit/builder.sh
+++ b/pkgs/build-support/fetchgit/builder.sh
@@ -16,6 +16,7 @@ $SHELL $fetcher --builder --url "$url" --out "$out" --rev "$rev" --name "$name"
   ${fetchTags:+--fetch-tags} \
   ${sparseCheckout:+--sparse-checkout "$sparseCheckout"} \
   ${nonConeMode:+--non-cone-mode} \
-  ${branchName:+--branch-name "$branchName"}
+  ${branchName:+--branch-name "$branchName"} \
+  ${rootDir:+--root-dir "$rootDir"}
 
 runHook postFetch
diff --git a/pkgs/build-support/fetchgit/default.nix b/pkgs/build-support/fetchgit/default.nix
index 374d55b0456c..f6099fddd984 100644
--- a/pkgs/build-support/fetchgit/default.nix
+++ b/pkgs/build-support/fetchgit/default.nix
@@ -8,12 +8,16 @@
 
 let
   urlToName =
-    url: rev:
+    {
+      url,
+      rev,
+      append,
+    }:
     let
       shortRev = lib.sources.shortRev rev;
       appendShort = lib.optionalString ((builtins.match "[a-f0-9]*" rev) != null) "-${shortRev}";
     in
-    "${lib.sources.urlToName url}${appendShort}";
+    "${lib.sources.urlToName url}${if append == "" then appendShort else append}";
 in
 
 lib.makeOverridable (
@@ -24,15 +28,20 @@ lib.makeOverridable (
       url,
       tag ? null,
       rev ? null,
-      name ? urlToName url (lib.revOrTag rev tag),
+      name ? urlToName {
+        inherit url;
+        rev = lib.revOrTag rev tag;
+        # when rootDir is specified, avoid invalidating the result when rev changes
+        append = if rootDir != "" then "-${lib.strings.sanitizeDerivationName rootDir}" else "";
+      },
       leaveDotGit ? deepClone || fetchTags,
       outputHash ? lib.fakeHash,
       outputHashAlgo ? null,
       fetchSubmodules ? true,
       deepClone ? false,
       branchName ? null,
-      sparseCheckout ? [ ],
-      nonConeMode ? false,
+      sparseCheckout ? lib.optional (rootDir != "") rootDir,
+      nonConeMode ? rootDir != "",
       nativeBuildInputs ? [ ],
       # Shell code executed before the file has been fetched.  This, in
       # particular, can do things like set NIX_PREFETCH_GIT_CHECKOUT_HOOK to
@@ -53,6 +62,8 @@ lib.makeOverridable (
       allowedRequisites ? null,
       # fetch all tags after tree (useful for git describe)
       fetchTags ? false,
+      # make this subdirectory the root of the result
+      rootDir ? "",
     }:
 
     /*
@@ -80,6 +91,7 @@ lib.makeOverridable (
 
     assert nonConeMode -> (sparseCheckout != [ ]);
     assert fetchTags -> leaveDotGit;
+    assert rootDir != "" -> !leaveDotGit;
 
     let
       revWithTag =
@@ -136,6 +148,7 @@ lib.makeOverridable (
           preFetch
           postFetch
           fetchTags
+          rootDir
           ;
         rev = revWithTag;
 
diff --git a/pkgs/build-support/fetchgit/tests.nix b/pkgs/build-support/fetchgit/tests.nix
index fd6aebc335f7..e3fdd5fb8672 100644
--- a/pkgs/build-support/fetchgit/tests.nix
+++ b/pkgs/build-support/fetchgit/tests.nix
@@ -97,4 +97,12 @@
       rm -rf .git
     '';
   };
+
+  rootDir = testers.invalidateFetcherByDrvHash fetchgit {
+    name = "fetchgit-with-rootdir";
+    url = "https://github.com/NixOS/nix";
+    rev = "9d9dbe6ed05854e03811c361a3380e09183f4f4a";
+    rootDir = "misc/systemd";
+    sha256 = "sha256-UhxHk4SrXYq7ZDMtXLig5SigpbITrVgkpFTmryuvpcM=";
+  };
 }