diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index 7e0ee9a..016bfac 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: [ 2.3, 2.4, 2.5, 2.6, 2.7, 3.0, 3.1, 3.2, head ]
+        ruby: [ 2.3, 2.4, 2.5, 2.6, 2.7, 3.0, 3.1, 3.2, 3.3, head ]
     steps:
       - uses: actions/checkout@v2
       - name: Setup ruby
diff --git a/README.md b/README.md
index 73a8f4d..1741f23 100644
--- a/README.md
+++ b/README.md
@@ -131,6 +131,7 @@ implementations:
 * Ruby 3.0
 * Ruby 3.1
 * Ruby 3.2
+* Ruby 3.3
 * [JRuby][]
 
 [jruby]: https://www.jruby.org/