diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 42116f7..a59c37b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -25,7 +25,7 @@ jobs:
 
       - uses: actions/setup-java@b843ebf9b913146b38da2eaa7aeddf76074ae1ad   # v5
         with:
-          java-version: '21'
+          java-version: '25'
           distribution: 'temurin'
           cache: 'gradle'
 
@@ -91,7 +91,7 @@ jobs:
 
       - uses: actions/setup-java@b843ebf9b913146b38da2eaa7aeddf76074ae1ad   # v5
         with:
-          java-version: '21'
+          java-version: '25'
           distribution: 'temurin'
           cache: 'gradle'
 
@@ -278,7 +278,7 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1            # v7.0.1
       - uses: actions/setup-java@b843ebf9b913146b38da2eaa7aeddf76074ae1ad          # v5
         with:
-          java-version: '21'
+          java-version: '25'
           distribution: 'temurin'
       - name: Submit Gradle dependency graph
         uses: gradle/actions/dependency-submission@8da46b539cd8fe6ab27ca75128919a18d757604c   # v6.4.1
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index c923399..19b4b77 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -30,7 +30,7 @@ jobs:
       - uses: actions/setup-java@b843ebf9b913146b38da2eaa7aeddf76074ae1ad            # v5
         if: matrix.language == 'java-kotlin'
         with:
-          java-version: '21'
+          java-version: '25'
           distribution: 'temurin'
       - uses: github/codeql-action/init@9b3254085494b55a0f7c4c2b3d2d52cc712ce370     # v4.39.1
         with:
diff --git a/.github/workflows/docker-publish.yml b/.github/workflows/docker-publish.yml
index 4e0f8e4..119abeb 100644
--- a/.github/workflows/docker-publish.yml
+++ b/.github/workflows/docker-publish.yml
@@ -28,11 +28,11 @@ jobs:
 
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1   # v7.0.1
 
-      - name: Set up JDK 21
+      - name: Set up JDK 25
         if: matrix.gradle_build
         uses: actions/setup-java@b843ebf9b913146b38da2eaa7aeddf76074ae1ad   # v5
         with:
-          java-version: '21'
+          java-version: '25'
           distribution: 'temurin'
           cache: 'gradle'
 
diff --git a/backend/Dockerfile b/backend/Dockerfile
index c8be647..3843e04 100644
--- a/backend/Dockerfile
+++ b/backend/Dockerfile
@@ -1,4 +1,4 @@
-# eclipse-temurin:21-jre-alpine
+# eclipse-temurin:25-jre-alpine
 FROM eclipse-temurin:25-jre-alpine@sha256:3c0a9084927a221ccd1d007fcaf614465672c0af37aaa834c5184483afe56d61
 # brotli-libs 1.2.0-r1 -> 1.2.1-r0 (CVE-2026-111497)
 RUN apk upgrade --no-cache p11-kit p11-kit-trust libexpat openssl libssl3 brotli-libs
diff --git a/backend/build.gradle.kts b/backend/build.gradle.kts
index 9c0795e..0e5ad39 100644
--- a/backend/build.gradle.kts
+++ b/backend/build.gradle.kts
@@ -24,7 +24,7 @@ plugins {
 
 group = "com.taskowolf"
 version = "0.0.1-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_21
+java.sourceCompatibility = JavaVersion.VERSION_25
 
 repositories {
     mavenCentral()
@@ -83,7 +83,7 @@ dependencies {
 tasks.withType<KotlinCompile> {
     compilerOptions {
         freeCompilerArgs.add("-Xjsr305=strict")
-        jvmTarget.set(JvmTarget.JVM_21)
+        jvmTarget.set(JvmTarget.JVM_25)
     }
 }
 
diff --git a/mkdocs/development.md b/mkdocs/development.md
index 3fb95ac..780ca19 100644
--- a/mkdocs/development.md
+++ b/mkdocs/development.md
@@ -2,7 +2,7 @@
 
 ## Prerequisites
 
-- JDK 21 (Temurin recommended)
+- JDK 25 (Temurin recommended)
 - Node.js 22.22+ (required by react-router v8 at build time)
 - Docker (for Testcontainers)