diff --git a/requirements-optional.txt b/requirements-optional.txt
index 15fba446d59..85d35f3d0f9 100644
--- a/requirements-optional.txt
+++ b/requirements-optional.txt
@@ -5,7 +5,7 @@ pre-commit==4.3.0
 ruff==0.14.2
 
 # For generating documentation.
-sphinx==8.2.3
+sphinx==9.1.0
 sphinx-autoapi==3.6.1
 
 # For 'manage' interactive shell