diff --git a/.github/actions/prepare-for-build/action.yml b/.github/actions/prepare-for-build/action.yml
index 92e751f60bb..1df2a44b634 100644
--- a/.github/actions/prepare-for-build/action.yml
+++ b/.github/actions/prepare-for-build/action.yml
@@ -6,7 +6,7 @@ name: Prepare Lucene build
 inputs:
    java-version:
      required: false
-     default: 17
+     default: 21
      description: "The default JDK version to set up."
 
    java-distribution:
diff --git a/.github/workflows/run-checks-all.yml b/.github/workflows/run-checks-all.yml
index 98248c9ad7d..3f899903dce 100644
--- a/.github/workflows/run-checks-all.yml
+++ b/.github/workflows/run-checks-all.yml
@@ -29,7 +29,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-latest ]
-        java: [ '17' ]
+        java: [ '21' ]
 
     runs-on: ${{ matrix.os }}
 
@@ -52,7 +52,7 @@ jobs:
         # windows-latest: fairly slow to build and results in odd errors (see LUCENE-10167)
         # macos-latest: a tad slower than ubuntu and pretty much the same (?) so leaving out.
         os: [ ubuntu-latest ]
-        java: [ '17' ]
+        java: [ '21' ]
 
     runs-on: ${{ matrix.os }}