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 10b99bd6f8e..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
@@ -59,9 +59,9 @@ public interface ElasticsearchConnectionDetails extends ConnectionDetails {
 
 	/**
 	 * APIKey for authentication with Elasticsearch.
-	 * @return APIKey for authentication with Elasticsearch or {@code null}
+	 * @return the API key for authentication with Elasticsearch or {@code null}
 	 */
-	default @Nullable String getAPIKey() {
+	default @Nullable String getApiKey() {
 		return null;
 	}
 
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 4189533bb42..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
@@ -48,10 +48,11 @@ public class ElasticsearchProperties {
 	 * Password for authentication with Elasticsearch.
 	 */
 	private @Nullable String password;
+
 	/**
-	 * APIKey for authentication with Elasticsearch.
+	 * API key for authentication with Elasticsearch.
 	 */
-	private @Nullable String APIKey;
+	private @Nullable String apiKey;
 
 	/**
 	 * Connection timeout used when communicating with Elasticsearch.
@@ -99,12 +100,12 @@ public class ElasticsearchProperties {
 		this.password = password;
 	}
 
-	public @Nullable String getAPIKey() {
-		return this.APIKey;
+	public @Nullable String getApiKey() {
+		return this.apiKey;
 	}
 
-	public void setAPIKey(@Nullable String APIKey) {
-		this.APIKey = APIKey;
+	public void setApiKey(@Nullable String apiKey) {
+		this.apiKey = apiKey;
 	}
 
 	public Duration getConnectionTimeout() {
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 253c7727fdf..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
@@ -102,10 +102,9 @@ 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()),
-				});
+			if (connectionDetails.getApiKey() != null) {
+				builder.setDefaultHeaders(
+						new Header[] { new BasicHeader("Authorization", "ApiKey " + connectionDetails.getApiKey()), });
 			}
 			builder.setHttpClientConfigCallback((httpClientBuilder) -> builderCustomizers.orderedStream()
 				.forEach((customizer) -> customizer.customize(httpClientBuilder)));
@@ -284,8 +283,8 @@ class ElasticsearchRestClientConfigurations {
 		}
 
 		@Override
-		public @Nullable String getAPIKey() {
-			return this.properties.getAPIKey();
+		public @Nullable String getApiKey() {
+			return this.properties.getApiKey();
 		}
 
 		@Override
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 d35091a1bf1..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
@@ -19,7 +19,6 @@ package org.springframework.boot.elasticsearch.autoconfigure;
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Optional;
 
 import co.elastic.clients.transport.rest5_client.low_level.Node;
 import co.elastic.clients.transport.rest5_client.low_level.Rest5Client;
@@ -49,7 +48,6 @@ import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.boot.testsupport.classpath.resources.WithPackageResources;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.web.client.RestClient;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.BDDMockito.then;
@@ -138,25 +136,6 @@ class ElasticsearchRestClientAutoConfigurationTests {
 		});
 	}
 
-	@Test
-	void configureUriWithAPiKey() {
-		this.contextRunner.withPropertyValues("spring.elasticsearch.uris=http://user@localhost:9200","spring.elasticsearch.apikey=some-apiKey").run((context) -> {
-			Rest5Client client = context.getBean(Rest5Client.class);
-			assertThat(client.getNodes().stream().map(Node::getHost).map(HttpHost::toString))
-					.containsExactly("http://localhost:9200");
-			assertThat(client)
-					.extracting("defaultHeaders", InstanceOfAssertFactories.list(Header.class))
-					.satisfies(( defaultHeaders) -> {
-						Optional<? extends Header> authHeader = defaultHeaders.stream()
-								.filter(x -> x.getName().equals("Authorization"))
-								.findFirst();
-						assertThat(authHeader).isPresent();
-						assertThat(authHeader.get().getValue()).isEqualTo("ApiKey some-apiKey");
-					});
-		});
-	}
-
-
 	@Test
 	void configureUriWithUsernameOnly() {
 		this.contextRunner.withPropertyValues("spring.elasticsearch.uris=http://user@localhost:9200").run((context) -> {
@@ -216,6 +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) -> {