diff --git a/build-tools/src/main/java/org/elasticsearch/gradle/testclusters/RunTask.java b/build-tools/src/main/java/org/elasticsearch/gradle/testclusters/RunTask.java
index 54bffd2a14b3d..9d2e6a7a2a024 100644
--- a/build-tools/src/main/java/org/elasticsearch/gradle/testclusters/RunTask.java
+++ b/build-tools/src/main/java/org/elasticsearch/gradle/testclusters/RunTask.java
@@ -42,7 +42,7 @@ public abstract class RunTask extends DefaultTestClustersTask {
 
     private Boolean debug = false;
     private Boolean cliDebug = false;
-    private Boolean entitlementsEnabled = false;
+
     private Boolean apmServerEnabled = false;
 
     private Boolean preserveData = false;
@@ -74,9 +74,7 @@ public void setCliDebug(boolean enabled) {
         option = "entitlements",
         description = "Use the Entitlements agent system in place of SecurityManager to enforce sandbox policies."
     )
-    public void setEntitlementsEnabled(boolean enabled) {
-        this.entitlementsEnabled = enabled;
-    }
+    public void setEntitlementsEnabled(boolean enabled) {}
 
     @Input
     public Boolean getDebug() {
@@ -90,7 +88,7 @@ public Boolean getCliDebug() {
 
     @Input
     public Boolean getEntitlementsEnabled() {
-        return entitlementsEnabled;
+        return true;
     }
 
     @Input
@@ -240,9 +238,7 @@ else if (node.getSettingKeys().contains("telemetry.metrics.enabled") == false) {
         if (cliDebug) {
             enableCliDebug();
         }
-        if (entitlementsEnabled) {
-            enableEntitlements();
-        }
+        enableEntitlements();
     }
 
     @TaskAction
diff --git a/distribution/tools/server-cli/src/main/java/org/elasticsearch/server/cli/SystemJvmOptions.java b/distribution/tools/server-cli/src/main/java/org/elasticsearch/server/cli/SystemJvmOptions.java
index 456e9e6303078..cf9aad6762c76 100644
--- a/distribution/tools/server-cli/src/main/java/org/elasticsearch/server/cli/SystemJvmOptions.java
+++ b/distribution/tools/server-cli/src/main/java/org/elasticsearch/server/cli/SystemJvmOptions.java
@@ -11,7 +11,6 @@
 
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.concurrent.EsExecutors;
-import org.elasticsearch.core.Booleans;
 import org.elasticsearch.jdk.RuntimeVersionFeature;
 
 import java.io.IOException;
@@ -28,9 +27,8 @@ static List<String> systemJvmOptions(Settings nodeSettings, final Map<String, St
         String distroType = sysprops.get("es.distribution.type");
         String javaType = sysprops.get("es.java.type");
         boolean isHotspot = sysprops.getOrDefault("sun.management.compiler", "").contains("HotSpot");
-        boolean entitlementsExplicitlyEnabled = Booleans.parseBoolean(sysprops.getOrDefault("es.entitlements.enabled", "true"));
-        // java 24+ only supports entitlements, but it may be enabled on earlier versions explicitly
-        boolean useEntitlements = RuntimeVersionFeature.isSecurityManagerAvailable() == false || entitlementsExplicitlyEnabled;
+
+        boolean useEntitlements = true;
         return Stream.of(
             Stream.of(
                 /*
diff --git a/docs/changelog/125117.yaml b/docs/changelog/125117.yaml
new file mode 100644
index 0000000000000..23395d6439044
--- /dev/null
+++ b/docs/changelog/125117.yaml
@@ -0,0 +1,8 @@
+pr: 125117
+summary: "Permanently switch from Java SecurityManager to Entitlements.
+  The Java SecurityManager has been deprecated since Java 17, and it is now completely disabled in Java 24. In order
+  to retain an similar level of protection, Elasticsearch implemented its own protection mechanism, Entitlements.
+  Starting with this version, Entitlements will permanently replace the Java SecurityManager."
+area: Infra/Core
+type: upgrade
+issues: []
diff --git a/modules/ingest-attachment/src/main/java/org/elasticsearch/ingest/attachment/TikaImpl.java b/modules/ingest-attachment/src/main/java/org/elasticsearch/ingest/attachment/TikaImpl.java
index 1b8bf67ff6fec..13447b620d14b 100644
--- a/modules/ingest-attachment/src/main/java/org/elasticsearch/ingest/attachment/TikaImpl.java
+++ b/modules/ingest-attachment/src/main/java/org/elasticsearch/ingest/attachment/TikaImpl.java
@@ -18,11 +18,9 @@
 import org.apache.tika.parser.ParserDecorator;
 import org.elasticsearch.SpecialPermission;
 import org.elasticsearch.bootstrap.FilePermissionUtils;
-import org.elasticsearch.core.Booleans;
 import org.elasticsearch.core.PathUtils;
 import org.elasticsearch.core.SuppressForbidden;
 import org.elasticsearch.jdk.JarHell;
-import org.elasticsearch.jdk.RuntimeVersionFeature;
 
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
@@ -129,9 +127,7 @@ static String parse(final byte content[], final Metadata metadata, final int lim
         : null;
 
     private static boolean isUsingSecurityManager() {
-        boolean entitlementsEnabled = Booleans.parseBoolean(System.getProperty("es.entitlements.enabled"), false)
-            || RuntimeVersionFeature.isSecurityManagerAvailable() == false;
-        return entitlementsEnabled == false;
+        return false;
     }
 
     // compute some minimal permissions for parsers. they only get r/w access to the java temp directory,
diff --git a/server/src/main/java/org/elasticsearch/bootstrap/Elasticsearch.java b/server/src/main/java/org/elasticsearch/bootstrap/Elasticsearch.java
index d09ea4dadf19d..06d01aef32e47 100644
--- a/server/src/main/java/org/elasticsearch/bootstrap/Elasticsearch.java
+++ b/server/src/main/java/org/elasticsearch/bootstrap/Elasticsearch.java
@@ -29,7 +29,6 @@
 import org.elasticsearch.common.transport.BoundTransportAddress;
 import org.elasticsearch.common.util.concurrent.RunOnce;
 import org.elasticsearch.core.AbstractRefCounted;
-import org.elasticsearch.core.Booleans;
 import org.elasticsearch.core.CheckedConsumer;
 import org.elasticsearch.core.IOUtils;
 import org.elasticsearch.core.SuppressForbidden;
@@ -129,9 +128,8 @@ private static Bootstrap initPhase1() {
         final PrintStream out = getStdout();
         final PrintStream err = getStderr();
         final ServerArgs args;
-        final boolean entitlementsEnabled = Booleans.parseBoolean(System.getProperty("es.entitlements.enabled", "true"));
-        // java 24+ only supports entitlements, but it may be enabled on earlier versions explicitly
-        final boolean useEntitlements = RuntimeVersionFeature.isSecurityManagerAvailable() == false || entitlementsEnabled;
+
+        final boolean useEntitlements = true;
         try {
             initSecurityProperties();
 
diff --git a/x-pack/qa/security-example-spi-extension/src/main/java/org/elasticsearch/example/ExampleSecurityExtension.java b/x-pack/qa/security-example-spi-extension/src/main/java/org/elasticsearch/example/ExampleSecurityExtension.java
index 5d8684bf32f89..3dbc4c1bf186f 100644
--- a/x-pack/qa/security-example-spi-extension/src/main/java/org/elasticsearch/example/ExampleSecurityExtension.java
+++ b/x-pack/qa/security-example-spi-extension/src/main/java/org/elasticsearch/example/ExampleSecurityExtension.java
@@ -36,7 +36,7 @@
 public class ExampleSecurityExtension implements SecurityExtension {
 
     static {
-        final boolean useEntitlements = Boolean.parseBoolean(System.getProperty("es.entitlements.enabled"));
+        final boolean useEntitlements = true;
         if (useEntitlements == false && RuntimeVersionFeature.isSecurityManagerAvailable()) {
             // check that the extension's policy works.
             AccessController.doPrivileged((PrivilegedAction<Void>) () -> {