diff --git a/oauth2/oauth2-resource-server/src/main/java/org/springframework/security/oauth2/server/resource/introspection/SpringReactiveOpaqueTokenIntrospector.java b/oauth2/oauth2-resource-server/src/main/java/org/springframework/security/oauth2/server/resource/introspection/SpringReactiveOpaqueTokenIntrospector.java
index bdd3f8d634b..a1b809f2491 100644
--- a/oauth2/oauth2-resource-server/src/main/java/org/springframework/security/oauth2/server/resource/introspection/SpringReactiveOpaqueTokenIntrospector.java
+++ b/oauth2/oauth2-resource-server/src/main/java/org/springframework/security/oauth2/server/resource/introspection/SpringReactiveOpaqueTokenIntrospector.java
@@ -268,6 +268,7 @@ default List<String> getScopes() {
 	 * Used to build {@link SpringReactiveOpaqueTokenIntrospector}.
 	 *
 	 * @author Ngoc Nhan
+	 * @author Andrey Litvitski
 	 * @since 6.5
 	 */
 	public static final class Builder {
@@ -278,6 +279,8 @@ public static final class Builder {
 
 		private String clientSecret;
 
+		private WebClient.Builder webClientBuilder;
+
 		private Builder(String introspectionUri) {
 			this.introspectionUri = introspectionUri;
 		}
@@ -308,13 +311,31 @@ public Builder clientSecret(String clientSecret) {
 			return this;
 		}
 
+		/**
+		 * The builder will use the provided {@link WebClient.Builder} to build the
+		 * {@link WebClient} used for token introspection requests. If not provided, a
+		 * default builder will be used.
+		 * @param webClientBuilder The {@link WebClient.Builder} to customize the HTTP
+		 * client
+		 * @return the {@link SpringReactiveOpaqueTokenIntrospector.Builder}
+		 * @since 6.5
+		 */
+		public Builder webClientBuilder(WebClient.Builder webClientBuilder) {
+			Assert.notNull(webClientBuilder, "webClientBuilder cannot be null");
+			this.webClientBuilder = webClientBuilder;
+			return this;
+		}
+
 		/**
 		 * Creates a {@code SpringReactiveOpaqueTokenIntrospector}
 		 * @return the {@link SpringReactiveOpaqueTokenIntrospector}
 		 * @since 6.5
 		 */
 		public SpringReactiveOpaqueTokenIntrospector build() {
-			WebClient webClient = WebClient.builder()
+			if (this.webClientBuilder == null) {
+				this.webClientBuilder = WebClient.builder();
+			}
+			WebClient webClient = this.webClientBuilder
 				.defaultHeaders((h) -> h.setBasicAuth(this.clientId, this.clientSecret))
 				.build();
 			return new SpringReactiveOpaqueTokenIntrospector(this.introspectionUri, webClient);
diff --git a/oauth2/oauth2-resource-server/src/test/java/org/springframework/security/oauth2/server/resource/introspection/SpringReactiveOpaqueTokenIntrospectorTests.java b/oauth2/oauth2-resource-server/src/test/java/org/springframework/security/oauth2/server/resource/introspection/SpringReactiveOpaqueTokenIntrospectorTests.java
index 8f05bd12207..93b0aee0e86 100644
--- a/oauth2/oauth2-resource-server/src/test/java/org/springframework/security/oauth2/server/resource/introspection/SpringReactiveOpaqueTokenIntrospectorTests.java
+++ b/oauth2/oauth2-resource-server/src/test/java/org/springframework/security/oauth2/server/resource/introspection/SpringReactiveOpaqueTokenIntrospectorTests.java
@@ -297,6 +297,7 @@ public void introspectWithEncodeClientCredentialsThenOk() throws Exception {
 				.withIntrospectionUri(introspectUri)
 				.clientId("client&1")
 				.clientSecret("secret@$2")
+				.webClientBuilder(WebClient.builder())
 				.build();
 			OAuth2AuthenticatedPrincipal authority = introspectionClient.introspect("token").block();
 			// @formatter:off