diff --git a/.github/workflows/doc-tests.yml b/.github/workflows/doc-tests.yml
index c7b2fa399..fb407d505 100644
--- a/.github/workflows/doc-tests.yml
+++ b/.github/workflows/doc-tests.yml
@@ -46,7 +46,7 @@ jobs:
         submodules: recursive
     - uses: actions/setup-python@83679a892e2d95755f2dac6acb0bfd1e9ac5d548 # v6.1.0
       with:
-        python-version: 3.11
+        python-version: 3.12
         architecture: 'x64'
     - name: Install dependencies
       # TODO: find way to split up dependencies
diff --git a/.readthedocs.yml b/.readthedocs.yml
index 112800323..80ec1b22e 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -9,7 +9,7 @@ version: 2
 build:
   os: ubuntu-22.04
   tools:
-    python: "3.11"
+    python: "3.12"
 
 # Build documentation in the doc/ directory with Sphinx
 sphinx:
diff --git a/doc/requirements.txt b/doc/requirements.txt
index ae2d2e0e5..26973d407 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,5 +1,5 @@
 # sphinx version requirement for readthedocs.
-sphinx==8.2.3
+sphinx==9.1.0
 sphinx-rtd-theme==3.1.0
 sphinxcontrib-spelling==8.0.0
 certifi>=2023.7.22 # not directly required, pinned by Snyk to avoid a vulnerability