diff --git a/.changeset/metal-needles-shout.md b/.changeset/metal-needles-shout.md
new file mode 100644
index 0000000000..4ea11e12ea
--- /dev/null
+++ b/.changeset/metal-needles-shout.md
@@ -0,0 +1,5 @@
+---
+"@astrojs/starlight": patch
+---
+
+Fix false positive in sidebar autogeneration logic
diff --git a/packages/starlight/utils/navigation.ts b/packages/starlight/utils/navigation.ts
index ae4f918bf8..1d5a176469 100644
--- a/packages/starlight/utils/navigation.ts
+++ b/packages/starlight/utils/navigation.ts
@@ -65,7 +65,13 @@ function groupFromAutogenerateConfig(
 ): Group {
   const { directory } = item.autogenerate;
   const localeDir = locale ? locale + '/' + directory : directory;
-  const dirDocs = routes.filter((doc) => doc.slug.startsWith(localeDir));
+  const dirDocs = routes.filter(
+    (doc) =>
+      // Match against `foo.md` or `foo/index.md`.
+      doc.slug === localeDir ||
+      // Match against `foo/anything/else.md`.
+      doc.slug.startsWith(localeDir + '/')
+  );
   const tree = treeify(dirDocs, localeDir);
   return {
     type: 'group',