diff --git a/test/src/main/java/org/springframework/security/test/web/reactive/server/SecurityMockServerConfigurers.java b/test/src/main/java/org/springframework/security/test/web/reactive/server/SecurityMockServerConfigurers.java
index bed8e62378..2510cd1c9b 100644
--- a/test/src/main/java/org/springframework/security/test/web/reactive/server/SecurityMockServerConfigurers.java
+++ b/test/src/main/java/org/springframework/security/test/web/reactive/server/SecurityMockServerConfigurers.java
@@ -783,6 +783,7 @@ public class SecurityMockServerConfigurers {
 			mockOAuth2Client()
 					.accessToken(this.accessToken)
 					.clientRegistration(this.clientRegistration)
+					.principalName(token.getPrincipal().getName())
 					.beforeServerCreated(builder);
 			mockAuthentication(getToken()).beforeServerCreated(builder);
 		}
@@ -1028,6 +1029,7 @@ public class SecurityMockServerConfigurers {
 	public final static class OAuth2ClientMutator implements WebTestClientConfigurer, MockServerConfigurer {
 		private String registrationId = "test";
 		private ClientRegistration clientRegistration;
+		private String principalName = "user";
 		private OAuth2AccessToken accessToken = new OAuth2AccessToken(OAuth2AccessToken.TokenType.BEARER,
 				"access-token", null, null, Collections.singleton("read"));
 
@@ -1068,6 +1070,18 @@ public class SecurityMockServerConfigurers {
 			return this;
 		}
 
+		/**
+		 * Use this as the resource owner's principal name
+		 *
+		 * @param principalName the resource owner's principal name
+		 * @return the {@link OAuth2ClientMutator} for further configuration
+		 */
+		public OAuth2ClientMutator principalName(String principalName) {
+			Assert.notNull(principalName, "principalName cannot be null");
+			this.principalName = principalName;
+			return this;
+		}
+
 		/**
 		 * Use this {@link OAuth2AccessToken}
 		 *
@@ -1110,7 +1124,7 @@ public class SecurityMockServerConfigurers {
 				throw new IllegalArgumentException("Please specify a ClientRegistration via one " +
 						"of the clientRegistration methods");
 			}
-			return new OAuth2AuthorizedClient(this.clientRegistration, "user", this.accessToken);
+			return new OAuth2AuthorizedClient(this.clientRegistration, this.principalName, this.accessToken);
 		}
 
 		private ClientRegistration.Builder clientRegistrationBuilder() {
diff --git a/test/src/main/java/org/springframework/security/test/web/servlet/request/SecurityMockMvcRequestPostProcessors.java b/test/src/main/java/org/springframework/security/test/web/servlet/request/SecurityMockMvcRequestPostProcessors.java
index ed9f41d148..c80bb9cfc5 100644
--- a/test/src/main/java/org/springframework/security/test/web/servlet/request/SecurityMockMvcRequestPostProcessors.java
+++ b/test/src/main/java/org/springframework/security/test/web/servlet/request/SecurityMockMvcRequestPostProcessors.java
@@ -1401,6 +1401,7 @@ public final class SecurityMockMvcRequestPostProcessors {
 			request = new AuthenticationRequestPostProcessor(token).postProcessRequest(request);
 			return new OAuth2ClientRequestPostProcessor()
 					.clientRegistration(this.clientRegistration)
+					.principalName(oauth2User.getName())
 					.accessToken(this.accessToken)
 					.postProcessRequest(request);
 		}
@@ -1587,6 +1588,7 @@ public final class SecurityMockMvcRequestPostProcessors {
 	public final static class OAuth2ClientRequestPostProcessor implements RequestPostProcessor {
 		private String registrationId = "test";
 		private ClientRegistration clientRegistration;
+		private String principalName = "user";
 		private OAuth2AccessToken accessToken = new OAuth2AccessToken(OAuth2AccessToken.TokenType.BEARER,
 				"access-token", null, null, Collections.singleton("read"));
 
@@ -1624,6 +1626,18 @@ public final class SecurityMockMvcRequestPostProcessors {
 			return this;
 		}
 
+		/**
+		 * Use this as the resource owner's principal name
+		 *
+		 * @param principalName the resource owner's principal name
+		 * @return the {@link OAuth2ClientRequestPostProcessor} for further configuration
+		 */
+		public OAuth2ClientRequestPostProcessor principalName(String principalName) {
+			Assert.notNull(principalName, "principalName cannot be null");
+			this.principalName = principalName;
+			return this;
+		}
+
 		/**
 		 * Use this {@link OAuth2AccessToken}
 		 *
@@ -1642,7 +1656,7 @@ public final class SecurityMockMvcRequestPostProcessors {
 						"of the clientRegistration methods");
 			}
 			OAuth2AuthorizedClient client = new OAuth2AuthorizedClient
-					(this.clientRegistration, "user", this.accessToken);
+					(this.clientRegistration, this.principalName, this.accessToken);
 			OAuth2AuthorizedClientRepository authorizedClientRepository =
 					new HttpSessionOAuth2AuthorizedClientRepository();
 			authorizedClientRepository.saveAuthorizedClient(client, null, request, new MockHttpServletResponse());
diff --git a/test/src/test/java/org/springframework/security/test/web/reactive/server/SecurityMockServerConfigurersOAuth2ClientTests.java b/test/src/test/java/org/springframework/security/test/web/reactive/server/SecurityMockServerConfigurersOAuth2ClientTests.java
index f15ee4eb95..8515e02f99 100644
--- a/test/src/test/java/org/springframework/security/test/web/reactive/server/SecurityMockServerConfigurersOAuth2ClientTests.java
+++ b/test/src/test/java/org/springframework/security/test/web/reactive/server/SecurityMockServerConfigurersOAuth2ClientTests.java
@@ -134,6 +134,16 @@ public class SecurityMockServerConfigurersOAuth2ClientTests extends AbstractMock
 		assertThat(client.getRefreshToken()).isNull();
 	}
 
+	@Test
+	public void oauth2ClientWhenPrincipalNameThenUses() throws Exception {
+		this.client.mutateWith(mockOAuth2Client("registration-id")
+				.principalName("test-subject"))
+				.get().uri("/client")
+				.exchange()
+				.expectStatus().isOk()
+				.expectBody(String.class).isEqualTo("test-subject");
+	}
+
 	@Test
 	public void oauth2ClientWhenAccessTokenThenUses()
 			throws Exception {
diff --git a/test/src/test/java/org/springframework/security/test/web/servlet/request/SecurityMockMvcRequestPostProcessorsOAuth2ClientTests.java b/test/src/test/java/org/springframework/security/test/web/servlet/request/SecurityMockMvcRequestPostProcessorsOAuth2ClientTests.java
index 39e4dda9ea..b80f491743 100644
--- a/test/src/test/java/org/springframework/security/test/web/servlet/request/SecurityMockMvcRequestPostProcessorsOAuth2ClientTests.java
+++ b/test/src/test/java/org/springframework/security/test/web/servlet/request/SecurityMockMvcRequestPostProcessorsOAuth2ClientTests.java
@@ -123,6 +123,13 @@ public class SecurityMockMvcRequestPostProcessorsOAuth2ClientTests {
 				.andExpect(content().string("client-id"));
 	}
 
+	@Test
+	public void oauth2ClientWhenPrincipalNameThenUses() throws Exception {
+		this.mvc.perform(get("/principal-name")
+				.with(oauth2Client("registration-id").principalName("test-subject")))
+				.andExpect(content().string("test-subject"));
+	}
+
 	@Test
 	public void oauth2ClientWhenAccessTokenThenUses() throws Exception {
 		OAuth2AccessToken accessToken = noScopes();
@@ -161,6 +168,11 @@ public class SecurityMockMvcRequestPostProcessorsOAuth2ClientTests {
 				return authorizedClient.getAccessToken().getTokenValue();
 			}
 
+			@GetMapping("/principal-name")
+			String principalName(@RegisteredOAuth2AuthorizedClient("registration-id") OAuth2AuthorizedClient authorizedClient) {
+				return authorizedClient.getPrincipalName();
+			}
+
 			@GetMapping("/client-id")
 			String clientId(@RegisteredOAuth2AuthorizedClient("registration-id") OAuth2AuthorizedClient authorizedClient) {
 				return authorizedClient.getClientRegistration().getClientId();