diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 90c7b534ff5a..d7d2f2968041 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -40,14 +40,12 @@ jobs:
       # When we specify multiple JDKs, the final one becomes the default, which is used to execute Maven itself.
       # Our Maven configuration then specifies different JDKs to use for some of the steps:
       # - 11 (sometimes) to *download* to support anyone who runs JDiff or our Gradle integration tests (including our doc snapshots and our Java 11 CI test run) but not to use directly
-      # - 21 for building Javadoc
-      # - 23 for running javac (to help people who build Guava locally and might not use a recent JDK to run Maven)
+      # - 23 for running Javadoc and javac (to help people who build Guava locally and might not use a recent JDK to run Maven)
       - name: 'Set up JDKs'
         uses: actions/setup-java@8df1039502a15bceb9433410b1a100fbe190c53b # v4.5.0
         with:
           java-version: |
             ${{ matrix.java }}
-            21
             23
           distribution: 'temurin'
           cache: 'maven'
@@ -80,9 +78,7 @@ jobs:
         with:
           # For discussion, see the first setup-java block.
           # The publish-snapshot workflow doesn't run tests, so we don't have to care which version Maven would select for that step.
-          java-version: |
-            21
-            23
+          java-version: 23
           distribution: 'temurin'
           cache: 'maven'
       - name: 'Publish'
@@ -109,7 +105,6 @@ jobs:
           # But we need Java 11 for JDiff.
           java-version: |
             11
-            21
             23
           distribution: 'temurin'
           cache: 'maven'
diff --git a/android/pom.xml b/android/pom.xml
index a3bda4530e90..cc13ab35e13a 100644
--- a/android/pom.xml
+++ b/android/pom.xml
@@ -199,20 +199,6 @@
             rm -rf ~/.m2/jdks/ ~/.m2/toolchains.xml
             (But don't run that if you have put something into ~/.m2/toolchains.xml yourself.)
             -->
-            <execution>
-              <id>download-21</id>
-              <goals>
-                <goal>toolchain</goal>
-              </goals>
-              <configuration>
-                <toolchains>
-                  <jdk>
-                    <version>21</version>
-                    <vendor>temurin</vendor>
-                  </jdk>
-                </toolchains>
-              </configuration>
-            </execution>
             <execution>
               <id>download-23-and-surefire-version</id>
               <goals>
@@ -329,8 +315,7 @@
           <version>3.11.2</version>
           <configuration>
             <jdkToolchain>
-              <version>21</version>
-              <vendor>temurin</vendor>
+              <version>23</version>
             </jdkToolchain>
             <quiet>true</quiet>
             <notimestamp>true</notimestamp>
diff --git a/pom.xml b/pom.xml
index 12a3daa9dfd5..1671e0485749 100644
--- a/pom.xml
+++ b/pom.xml
@@ -200,20 +200,6 @@
             rm -rf ~/.m2/jdks/ ~/.m2/toolchains.xml
             (But don't run that if you have put something into ~/.m2/toolchains.xml yourself.)
             -->
-            <execution>
-              <id>download-21</id>
-              <goals>
-                <goal>toolchain</goal>
-              </goals>
-              <configuration>
-                <toolchains>
-                  <jdk>
-                    <version>21</version>
-                    <vendor>temurin</vendor>
-                  </jdk>
-                </toolchains>
-              </configuration>
-            </execution>
             <execution>
               <id>download-23-and-surefire-version</id>
               <goals>
@@ -324,8 +310,7 @@
           <version>3.11.2</version>
           <configuration>
             <jdkToolchain>
-              <version>21</version>
-              <vendor>temurin</vendor>
+              <version>23</version>
             </jdkToolchain>
             <quiet>true</quiet>
             <notimestamp>true</notimestamp>