diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 00adb4b7..cf0de0fa 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,7 +16,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: 'temurin' # See 'Supported distributions' for available options
-          java-version: '17'
+          java-version: '21'
           cache: 'gradle'
       - name: Build
         run: ./gradlew check
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 73a369ba..5cc7af52 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -57,7 +57,7 @@ jobs:
     - uses: actions/setup-java@v4
       with:
         distribution: 'temurin' # See 'Supported distributions' for available options
-        java-version: '17'
+        java-version: '21'
 
 
     # Autobuild attempts to build any compiled languages  (C/C++, C#, Go, or Java).
diff --git a/.github/workflows/swagger.yml b/.github/workflows/swagger.yml
index 5a9a610d..0361a082 100644
--- a/.github/workflows/swagger.yml
+++ b/.github/workflows/swagger.yml
@@ -16,11 +16,11 @@ jobs:
           path: ~/.gradle/caches
           key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle') }}
           restore-keys: ${{ runner.os }}-gradle-
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v4
         with:
           distribution: "temurin" # See 'Supported distributions' for available options
-          java-version: 17
+          java-version: 21
           cache: "gradle"
       - name: Run Swagger Publisher
         run: ./gradlew integration --tests uk.gov.hmcts.darts.common.config.SwaggerPublisherTest
diff --git a/Dockerfile b/Dockerfile
index 3eb0b3c2..6c09cb66 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,7 +3,7 @@
 ARG APP_INSIGHTS_AGENT_VERSION=3.5.3
 
  # renovate: datasource=github-releases depName=microsoft/ApplicationInsights-Java
-FROM hmctspublic.azurecr.io/base/java:17-distroless
+FROM hmctspublic.azurecr.io/base/java:21-distroless
 
 COPY lib/applicationinsights.json /opt/app/
 COPY build/libs/darts-gateway.jar /opt/app/
diff --git a/README.md b/README.md
index 350f8ac3..f58bea07 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,11 @@
 # darts-gateway
+This application acts as a layer between external services sending SOAP requests and translating into JSON forwarding onto the DARTS-API.
+
+# Building and deploying the application
+
+## Prerequisites
+
+- [Java 21](https://www.oracle.com/java)
 
 # SoapUI
 
diff --git a/build.gradle b/build.gradle
index d9dc20ec..f09c6318 100644
--- a/build.gradle
+++ b/build.gradle
@@ -22,7 +22,7 @@ version = '0.0.1'
 
 java {
   toolchain {
-    languageVersion = JavaLanguageVersion.of(17)
+    languageVersion = JavaLanguageVersion.of(21)
   }
 }
 
diff --git a/context/build.gradle b/context/build.gradle
index f037dd82..5756f41a 100644
--- a/context/build.gradle
+++ b/context/build.gradle
@@ -13,7 +13,7 @@ repositories {
 
 java {
   toolchain {
-    languageVersion = JavaLanguageVersion.of(17)
+    languageVersion = JavaLanguageVersion.of(21)
   }
 }