diff --git a/spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/NettyRoutingFilter.java b/spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/NettyRoutingFilter.java
index baf274f0..72c885d4 100644
--- a/spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/NettyRoutingFilter.java
+++ b/spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/NettyRoutingFilter.java
@@ -122,6 +122,10 @@ public class NettyRoutingFilter implements GlobalFilter, Ordered {
 				String host = request.getHeaders().getFirst(HttpHeaders.HOST);
 				headers.add(HttpHeaders.HOST, host);
 			}
+			else {
+				// let Netty set it based on hostname
+				headers.remove(HttpHeaders.HOST);
+			}
 		}).request(method).uri(url).send((req, nettyOutbound) -> {
 			if (log.isTraceEnabled()) {
 				nettyOutbound.withConnection(connection -> log.trace(
diff --git a/spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/NettyRoutingFilterIntegrationTests.java b/spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/NettyRoutingFilterIntegrationTests.java
index 08d7a997..16845423 100644
--- a/spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/NettyRoutingFilterIntegrationTests.java
+++ b/spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/NettyRoutingFilterIntegrationTests.java
@@ -27,6 +27,7 @@ import org.springframework.context.annotation.Import;
 import org.springframework.http.HttpStatus;
 import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.web.reactive.server.WebTestClient;
 
 import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
 
@@ -46,6 +47,18 @@ public class NettyRoutingFilterIntegrationTests extends BaseWebClientTests {
 				.isEqualTo("Response took longer than timeout: PT3S");
 	}
 
+	@Test
+	public void outboundHostHeaderNotOverwrittenByInbound() {
+		// different base url to have different host header in inbound / outbound requests
+		// Host: 127.0.0.1 -> request to Gateway, Host: localhost -> request from Gateway,
+		// resolved from lb://testservice
+		WebTestClient client = testClient.mutate().baseUrl("http://127.0.0.1:" + port)
+				.build();
+
+		client.get().uri("/headers").exchange().expectBody().jsonPath("$.headers.host")
+				.isEqualTo("localhost:" + port);
+	}
+
 	@EnableAutoConfiguration
 	@SpringBootConfiguration
 	@Import(DefaultTestConfig.class)