diff --git a/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchConnectionDetails.java b/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchConnectionDetails.java
index 6c3ae251162..e3ccd83381e 100644
--- a/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchConnectionDetails.java
+++ b/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchConnectionDetails.java
@@ -57,6 +57,14 @@ public interface ElasticsearchConnectionDetails extends ConnectionDetails {
 		return null;
 	}
 
+	/**
+	 * APIKey for authentication with Elasticsearch.
+	 * @return the API key for authentication with Elasticsearch or {@code null}
+	 */
+	default @Nullable String getApiKey() {
+		return null;
+	}
+
 	/**
 	 * Prefix added to the path of every request sent to Elasticsearch.
 	 * @return prefix added to the path of every request sent to Elasticsearch or
diff --git a/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchProperties.java b/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchProperties.java
index d6d98718686..1c5143cbe3c 100644
--- a/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchProperties.java
+++ b/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchProperties.java
@@ -49,6 +49,11 @@ public class ElasticsearchProperties {
 	 */
 	private @Nullable String password;
 
+	/**
+	 * API key for authentication with Elasticsearch.
+	 */
+	private @Nullable String apiKey;
+
 	/**
 	 * Connection timeout used when communicating with Elasticsearch.
 	 */
@@ -95,6 +100,14 @@ public class ElasticsearchProperties {
 		this.password = password;
 	}
 
+	public @Nullable String getApiKey() {
+		return this.apiKey;
+	}
+
+	public void setApiKey(@Nullable String apiKey) {
+		this.apiKey = apiKey;
+	}
+
 	public Duration getConnectionTimeout() {
 		return this.connectionTimeout;
 	}
diff --git a/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchRestClientConfigurations.java b/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchRestClientConfigurations.java
index 5ca31778274..ca6d738c237 100644
--- a/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchRestClientConfigurations.java
+++ b/module/spring-boot-elasticsearch/src/main/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchRestClientConfigurations.java
@@ -36,7 +36,9 @@ import org.apache.hc.client5.http.impl.auth.BasicCredentialsProvider;
 import org.apache.hc.client5.http.impl.nio.PoolingAsyncClientConnectionManagerBuilder;
 import org.apache.hc.client5.http.ssl.DefaultClientTlsStrategy;
 import org.apache.hc.client5.http.ssl.NoopHostnameVerifier;
+import org.apache.hc.core5.http.Header;
 import org.apache.hc.core5.http.HttpHost;
+import org.apache.hc.core5.http.message.BasicHeader;
 import org.apache.hc.core5.reactor.IOReactorConfig;
 import org.apache.hc.core5.reactor.ssl.SSLBufferMode;
 import org.apache.hc.core5.util.Timeout;
@@ -67,6 +69,7 @@ import org.springframework.util.StringUtils;
  * @author Moritz Halbritter
  * @author Andy Wilkinson
  * @author Phillip Webb
+ * @author Laura Trotta
  */
 class ElasticsearchRestClientConfigurations {
 
@@ -99,6 +102,10 @@ class ElasticsearchRestClientConfigurations {
 				.stream()
 				.map((node) -> new HttpHost(node.protocol().getScheme(), node.hostname(), node.port()))
 				.toArray(HttpHost[]::new));
+			if (connectionDetails.getApiKey() != null) {
+				builder.setDefaultHeaders(
+						new Header[] { new BasicHeader("Authorization", "ApiKey " + connectionDetails.getApiKey()), });
+			}
 			builder.setHttpClientConfigCallback((httpClientBuilder) -> builderCustomizers.orderedStream()
 				.forEach((customizer) -> customizer.customize(httpClientBuilder)));
 			builder.setConnectionManagerCallback((connectionManagerBuilder) -> builderCustomizers.orderedStream()
@@ -275,6 +282,11 @@ class ElasticsearchRestClientConfigurations {
 			return this.properties.getPassword();
 		}
 
+		@Override
+		public @Nullable String getApiKey() {
+			return this.properties.getApiKey();
+		}
+
 		@Override
 		public @Nullable String getPathPrefix() {
 			return this.properties.getPathPrefix();
diff --git a/module/spring-boot-elasticsearch/src/test/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchRestClientAutoConfigurationTests.java b/module/spring-boot-elasticsearch/src/test/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchRestClientAutoConfigurationTests.java
index a80a819d0d6..64e07a15532 100644
--- a/module/spring-boot-elasticsearch/src/test/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchRestClientAutoConfigurationTests.java
+++ b/module/spring-boot-elasticsearch/src/test/java/org/springframework/boot/elasticsearch/autoconfigure/ElasticsearchRestClientAutoConfigurationTests.java
@@ -33,6 +33,7 @@ import org.apache.hc.client5.http.config.RequestConfig;
 import org.apache.hc.client5.http.impl.async.HttpAsyncClientBuilder;
 import org.apache.hc.client5.http.impl.nio.PoolingAsyncClientConnectionManagerBuilder;
 import org.apache.hc.core5.function.Resolver;
+import org.apache.hc.core5.http.Header;
 import org.apache.hc.core5.http.HttpHost;
 import org.apache.hc.core5.http.config.Registry;
 import org.apache.hc.core5.util.Timeout;
@@ -62,6 +63,7 @@ import static org.mockito.Mockito.mock;
  * @author Andy Wilkinson
  * @author Moritz Halbritter
  * @author Phillip Webb
+ * @author Laura Trotta
  */
 class ElasticsearchRestClientAutoConfigurationTests {
 
@@ -193,6 +195,41 @@ class ElasticsearchRestClientAutoConfigurationTests {
 			});
 	}
 
+	@Test
+	void whenApiKeyIsConfiguredThenAuthorizationHeaderIsPresent() {
+		this.contextRunner.withPropertyValues("spring.elasticsearch.api-key=some-api-key").run((context) -> {
+			Rest5Client client = context.getBean(Rest5Client.class);
+			assertThat(client).extracting("defaultHeaders", InstanceOfAssertFactories.list(Header.class))
+				.satisfiesOnlyOnce((header) -> {
+					assertThat(header.getName().equals("Authorization"));
+					assertThat(header.getValue().equals("ApiKey some-api-key"));
+				});
+		});
+	}
+
+	@Test
+	void whenApiKeyAndUsernameAndPasswordAreConfiguredThenBothFormsOfCredentialsArePresent() {
+		this.contextRunner
+			.withPropertyValues("spring.elasticsearch.api-key=some-api-key", "spring.elasticsearch.username=alice",
+					"spring.elasticsearch.password=secret")
+			.run((context) -> {
+				Rest5Client client = context.getBean(Rest5Client.class);
+				assertThat(client).extracting("defaultHeaders", InstanceOfAssertFactories.list(Header.class))
+					.satisfiesOnlyOnce((header) -> {
+						assertThat(header.getName().equals("Authorization"));
+						assertThat(header.getValue().equals("ApiKey some-api-key"));
+					});
+				assertThat(client)
+					.extracting("client.credentialsProvider", InstanceOfAssertFactories.type(CredentialsProvider.class))
+					.satisfies((credentialsProvider) -> {
+						UsernamePasswordCredentials defaultCredentials = (UsernamePasswordCredentials) credentialsProvider
+							.getCredentials(new AuthScope(null, -1), null);
+						assertThat(defaultCredentials.getUserPrincipal().getName()).isEqualTo("alice");
+						assertThat(defaultCredentials.getUserPassword()).containsExactly("secret".toCharArray());
+					});
+			});
+	}
+
 	@Test
 	void configureWithCustomPathPrefix() {
 		this.contextRunner.withPropertyValues("spring.elasticsearch.path-prefix=/some/prefix").run((context) -> {