diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 84b4f09f9..c807e348e 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -20,7 +20,7 @@ jobs:
   Build-k-NN-Linux:
     strategy:
       matrix:
-        java: [11, 17]
+        java: [11, 17, 21]
 
     name: Build and Test k-NN Plugin on Linux
     runs-on: ubuntu-latest
@@ -57,7 +57,7 @@ jobs:
   Build-k-NN-MacOS:
     strategy:
       matrix:
-        java: [ 11, 17 ]
+        java: [ 11, 17, 21 ]
 
     name: Build and Test k-NN Plugin on MacOS
     needs: Get-CI-Image-Tag
@@ -84,7 +84,7 @@ jobs:
   Build-k-NN-Windows:
     strategy:
       matrix:
-        java: [ 11, 17 ]
+        java: [ 11, 17, 21 ]
 
     name: Build and Test k-NN Plugin on Windows
     needs: Get-CI-Image-Tag
diff --git a/.github/workflows/backwards_compatibility_tests_workflow.yml b/.github/workflows/backwards_compatibility_tests_workflow.yml
index 61cba5839..5357a4778 100644
--- a/.github/workflows/backwards_compatibility_tests_workflow.yml
+++ b/.github/workflows/backwards_compatibility_tests_workflow.yml
@@ -13,7 +13,7 @@ jobs:
   Restart-Upgrade-BWCTests-k-NN:
     strategy:
       matrix:
-        java: [ 11, 17 ]
+        java: [ 11, 17, 21 ]
         os: [ubuntu-latest]
         bwc_version : [ "2.0.1", "2.1.0", "2.2.1", "2.3.0", "2.4.1", "2.5.0", "2.6.0", "2.7.0", "2.8.0", "2.9.0", "2.10.0", "2.11.0-SNAPSHOT"]
         opensearch_version : [ "3.0.0-SNAPSHOT" ]
@@ -86,7 +86,7 @@ jobs:
   Rolling-Upgrade-BWCTests-k-NN:
     strategy:
       matrix:
-        java: [ 11, 17 ]
+        java: [ 11, 17, 21 ]
         os: [ubuntu-latest]
         bwc_version: [ "2.11.0-SNAPSHOT" ]
         opensearch_version: [ "3.0.0-SNAPSHOT" ]
diff --git a/.github/workflows/test_security.yml b/.github/workflows/test_security.yml
index 3813ff675..ff3ca1459 100644
--- a/.github/workflows/test_security.yml
+++ b/.github/workflows/test_security.yml
@@ -15,7 +15,7 @@ jobs:
   Build-ad:
     strategy:
       matrix:
-        java: [ 11,17 ]
+        java: [ 11,17,21 ]
         os: [ubuntu-latest]
       fail-fast: true