diff --git a/.github/workflows/alarm-logger-docker-image.yml b/.github/workflows/alarm-logger-docker-image.yml
index 2641320193..1e872f5b62 100644
--- a/.github/workflows/alarm-logger-docker-image.yml
+++ b/.github/workflows/alarm-logger-docker-image.yml
@@ -19,7 +19,7 @@ jobs:
       - name: Setup Maven and Java Action
         uses: s4u/setup-maven-action@v1.18.0
         with:
-          java-version: '17'
+          java-version: '21'
           maven-version: '3.9.6'
       - name: Build
         run: mvn --batch-mode install -DskipTests
@@ -30,10 +30,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - name: Set up JDK 17
+    - name: Set up JDK 21
       uses: actions/setup-java@v4
       with:
-        java-version: '17'
+        java-version: '21'
         distribution: 'temurin'
         cache: maven
     - name: Build with Maven
diff --git a/.github/workflows/alarm-server-docker-image.yml b/.github/workflows/alarm-server-docker-image.yml
index a304971639..44b90a3c62 100644
--- a/.github/workflows/alarm-server-docker-image.yml
+++ b/.github/workflows/alarm-server-docker-image.yml
@@ -19,7 +19,7 @@ jobs:
       - name: Setup Maven and Java Action
         uses: s4u/setup-maven-action@v1.18.0
         with:
-          java-version: '17'
+          java-version: '21'
           maven-version: '3.9.6'
       - name: Build
         run: mvn --batch-mode install -DskipTests
@@ -30,10 +30,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - name: Set up JDK 17
+    - name: Set up JDK 21
       uses: actions/setup-java@v4
       with:
-        java-version: '17'
+        java-version: '21'
         distribution: 'temurin'
         cache: maven
     - name: Build with Maven
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 8b1e890f3d..00ee599c99 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -14,7 +14,7 @@ jobs:
     - name: Setup Maven and Java Action
       uses: s4u/setup-maven-action@v1.18.0
       with:
-        java-version: '17'
+        java-version: '21'
         maven-version: '3.9.6'
     - name: Build
       run: mvn --batch-mode install -DskipTests
\ No newline at end of file
diff --git a/.github/workflows/build_latest.yml b/.github/workflows/build_latest.yml
index 6d39ae0918..72bc62f3be 100644
--- a/.github/workflows/build_latest.yml
+++ b/.github/workflows/build_latest.yml
@@ -18,7 +18,7 @@ jobs:
     - name: Setup Maven and Java Action
       uses: s4u/setup-maven-action@v1.18.0
       with:
-        java-version: '17'
+        java-version: '21'
         maven-version: '3.9.6'
     - name: Build
       run: mvn --batch-mode install -DskipTests
diff --git a/.github/workflows/build_swagger.yml b/.github/workflows/build_swagger.yml
index 3d2f764132..44ad301ac4 100644
--- a/.github/workflows/build_swagger.yml
+++ b/.github/workflows/build_swagger.yml
@@ -14,7 +14,7 @@ jobs:
     - name: Setup Maven and Java Action
       uses: s4u/setup-maven-action@v1.18.0
       with:
-        java-version: '17'
+        java-version: '21'
         maven-version: '3.9.6'
     - name: Get swagger.json
       run: |
diff --git a/.github/workflows/save-and-restore-docker-image.yml b/.github/workflows/save-and-restore-docker-image.yml
index 0a3f1cc6bc..239f06b1fc 100644
--- a/.github/workflows/save-and-restore-docker-image.yml
+++ b/.github/workflows/save-and-restore-docker-image.yml
@@ -19,10 +19,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - name: Set up JDK 17
+    - name: Set up JDK 21
       uses: actions/setup-java@v4
       with:
-        java-version: '17'
+        java-version: '21'
         distribution: 'temurin'
         cache: maven
     - name: Build with Maven
diff --git a/README.md b/README.md
index 22cc6c8e17..22f057cd9e 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,7 @@ https://control-system-studio.readthedocs.io
 
 
 ## Requirements
- - [JDK17 or later, suggested is OpenJDK](https://adoptium.net/en-GB/temurin/archive/?version=17).
+ - [JDK21 or later, suggested is OpenJDK](https://adoptium.net/en-GB/temurin/archive/?version=21).
  - [maven 3.x](https://maven.apache.org/) or [ant](http://ant.apache.org/)
 
 
@@ -27,7 +27,7 @@ mvn clean verify -f dependencies/pom.xml
 Define the JAVA_HOME environment variable to point to your Java installation directory. 
 Mac OS users should use something like:
 ```
-export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk-17.0.10+7/Contents/Home
+export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk-21.0.10+7/Contents/Home
 ```
 Verify through:
 ```
@@ -73,13 +73,13 @@ Download "Eclipse for Java Developers" from https://www.eclipse.org/downloads/pa
 
 Start Eclipse like this:
 
-    export JAVA_HOME=/path/to/your/jdk-17-or-later
+    export JAVA_HOME=/path/to/your/jdk-21-or-later
     export PATH="$JAVA_HOME/bin:$PATH"
     eclipse/eclipse -consoleLog
 
 Check Eclipse Preferences:
 
- * Java, Installed JREs: JDK 17-or-later should be the default
+ * Java, Installed JREs: JDK 21-or-later should be the default
  * Java, Compiler: JDK Compliance should be "9" or higher
 
 
@@ -112,7 +112,8 @@ In Help/Eclipse Marketplace, search for Maven Integration for Eclipse Luna or ne
 Use File/Import/Maven/Existing Maven Projects to import the phoebus source code.
 
 There can be a compiler error because the "JRE System Library" in the Package Explorer shows "[J2SE-1.4]".
-Right click on the affected projects (greeting-app, probe), Build Path, Configure Build Path, Libraries, Edit the JRE System Library to use the Workspace default (jdk-17).
+Right click on the affected projects (greeting-app, probe), Build Path, 
+Configure Build Path, Libraries, Edit the JRE System Library to use the Workspace default (jdk-21).
 Restart Eclipse IDE.
 
 Can now start product/src/main/java/org.phoebus.product/Launcher.java.
@@ -133,7 +134,7 @@ To run the Phoebus application:
 
 * Run | Edit Configurations...
 * Select + | Application
-* Module: Your JRE 17
+* Module: Your JRE 21
 * Classpath `-cp`: select `product` from drop-down
 * Main class: `org.phoebus.product.Launcher`
 * Set the name to Phoebus
diff --git a/app/alarm/audio-annunciator/pom.xml b/app/alarm/audio-annunciator/pom.xml
index 085313f76a..52466fa955 100644
--- a/app/alarm/audio-annunciator/pom.xml
+++ b/app/alarm/audio-annunciator/pom.xml
@@ -11,8 +11,8 @@
     <artifactId>app-alarm-audio-annunciator</artifactId>
 
     <properties>
-        <maven.compiler.source>17</maven.compiler.source>
-        <maven.compiler.target>17</maven.compiler.target>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
     </properties>
 
     <dependencies>
diff --git a/app/alarm/freetts-annunciator/pom.xml b/app/alarm/freetts-annunciator/pom.xml
index 58b9bbd018..9720465e6e 100644
--- a/app/alarm/freetts-annunciator/pom.xml
+++ b/app/alarm/freetts-annunciator/pom.xml
@@ -11,8 +11,8 @@
     <artifactId>app-alarm-freetts-annunciator</artifactId>
 
     <properties>
-        <maven.compiler.source>17</maven.compiler.source>
-        <maven.compiler.target>17</maven.compiler.target>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
     </properties>
 
     <dependencies>
diff --git a/app/display/actions/pom.xml b/app/display/actions/pom.xml
index 6fe4c3a7c8..42882c66d8 100644
--- a/app/display/actions/pom.xml
+++ b/app/display/actions/pom.xml
@@ -16,8 +16,8 @@
     <artifactId>app-display-actions</artifactId>
 
     <properties>
-        <maven.compiler.source>17</maven.compiler.source>
-        <maven.compiler.target>17</maven.compiler.target>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>
     <dependencies>
diff --git a/app/save-and-restore/util/pom.xml b/app/save-and-restore/util/pom.xml
index f7083fcdf3..d83f37a22d 100644
--- a/app/save-and-restore/util/pom.xml
+++ b/app/save-and-restore/util/pom.xml
@@ -12,8 +12,8 @@
     <artifactId>save-and-restore-util</artifactId>
 
     <properties>
-        <maven.compiler.source>17</maven.compiler.source>
-        <maven.compiler.target>17</maven.compiler.target>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
     </properties>
 
     <dependencies>
diff --git a/app/trends/archive-datasource/pom.xml b/app/trends/archive-datasource/pom.xml
index 988864edd9..459080208a 100644
--- a/app/trends/archive-datasource/pom.xml
+++ b/app/trends/archive-datasource/pom.xml
@@ -11,8 +11,8 @@
     <artifactId>app-trends-archive-datasource</artifactId>
 
     <properties>
-        <maven.compiler.source>17</maven.compiler.source>
-        <maven.compiler.target>17</maven.compiler.target>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
     </properties>
 
     <dependencies>
diff --git a/app/trends/archive-reader/pom.xml b/app/trends/archive-reader/pom.xml
index 21ce6b584f..fae8bb7959 100644
--- a/app/trends/archive-reader/pom.xml
+++ b/app/trends/archive-reader/pom.xml
@@ -12,8 +12,8 @@
     <artifactId>app-trends-archive-reader</artifactId>
 
     <properties>
-        <maven.compiler.source>17</maven.compiler.source>
-        <maven.compiler.target>17</maven.compiler.target>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
     </properties>
 
     <dependencies>
diff --git a/pom.xml b/pom.xml
index 06fbdab18d..1ec0204d00 100644
--- a/pom.xml
+++ b/pom.xml
@@ -89,7 +89,7 @@
     <derby.version>10.16.1.1</derby.version>
     <jython.version>2.7.4b1</jython.version>
     <jgit.version>6.9.0.202403050737-r</jgit.version>
-    <maven.compiler.target>17</maven.compiler.target>
+    <maven.compiler.target>21</maven.compiler.target>
     <activemq.client.version>5.18.4</activemq.client.version>
     <commons.compress.version>1.26.1</commons.compress.version>
     <!--suppress UnresolvedMavenProperty -->
@@ -101,8 +101,8 @@
         <artifactId>maven-compiler-plugin</artifactId>
         <version>3.6.2</version>
         <configuration>
-          <source>17</source>
-          <target>17</target>
+          <source>21</source>
+          <target>21</target>
           <fork>true</fork>
           <compilerArgs>
             <arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED</arg>
@@ -283,7 +283,7 @@
               <configuration>
                 <!-- add this to disable checking -->
                 <doclint>none</doclint>
-                <source>17</source>
+                <source>21</source>
               </configuration>
             </execution>
           </executions>
diff --git a/services/save-and-restore/README.md b/services/save-and-restore/README.md
index 7676e323c7..cd0c6bf1c4 100644
--- a/services/save-and-restore/README.md
+++ b/services/save-and-restore/README.md
@@ -4,7 +4,8 @@ The save-and-restore service implements service as a collection
 of REST endpoints. These can be used by clients to manage configurations (aka save sets) and
 snapshots, to compare snapshots and to restore PV values from snapshots.
 
-The service is packaged as a self-contained Spring Boot jar file. External dependencies are limited to a JVM (Java 17+)
+The service is packaged as a self-contained Spring Boot jar file. 
+External dependencies are limited to a JVM (Java 21+)
 and a running instance of Elasticsearch (8.x).
 
 # Build
diff --git a/services/save-and-restore/doc/index.rst b/services/save-and-restore/doc/index.rst
index 7e3990224a..af5d39aad2 100644
--- a/services/save-and-restore/doc/index.rst
+++ b/services/save-and-restore/doc/index.rst
@@ -5,7 +5,8 @@ The save-and-restore service implements service as a collection
 of REST endpoints. These can be used by clients to manage configurations (aka save sets) and
 snapshots, to compare snapshots and to restore PV values from snapshots.
 
-The service is packaged as a self-contained Spring Boot jar file. External dependencies are limited to a JVM (Java 17+)
+The service is packaged as a self-contained Spring Boot jar file.
+External dependencies are limited to a JVM (Java 21+)
 and a running instance of Elasticsearch (8.x).
 
 Running the service