diff --git a/libs/providers/flagd/README.md b/libs/providers/flagd/README.md
index 1506cf229..b1a3b405e 100644
--- a/libs/providers/flagd/README.md
+++ b/libs/providers/flagd/README.md
@@ -38,6 +38,7 @@ Options can be defined in the constructor or as environment variables. Construct
 | selector                               | FLAGD_SOURCE_SELECTOR          | string  | -                                                              |                  |
 | cache                                  | FLAGD_CACHE                    | string  | lru                                                            | lru, disabled    |
 | maxCacheSize                           | FLAGD_MAX_CACHE_SIZE           | int     | 1000                                                           |                  |
+| serviceAuthority                       | FLAGD_SERVICE_AUTHORITY        | string  | -                                                              | rpc, in-process  |
 
 #### Resolver type-specific Defaults
 
diff --git a/libs/providers/flagd/src/lib/configuration.spec.ts b/libs/providers/flagd/src/lib/configuration.spec.ts
index cd766356f..dac19c503 100644
--- a/libs/providers/flagd/src/lib/configuration.spec.ts
+++ b/libs/providers/flagd/src/lib/configuration.spec.ts
@@ -31,6 +31,7 @@ describe('Configuration', () => {
     const resolverType = 'in-process';
     const selector = 'app=weather';
     const offlineFlagSourcePath = '/tmp/flags.json';
+    const serviceAuthority = 'test-service2';
 
     process.env['FLAGD_HOST'] = host;
     process.env['FLAGD_PORT'] = `${port}`;
@@ -41,6 +42,7 @@ describe('Configuration', () => {
     process.env['FLAGD_SOURCE_SELECTOR'] = `${selector}`;
     process.env['FLAGD_RESOLVER'] = `${resolverType}`;
     process.env['FLAGD_OFFLINE_FLAG_SOURCE_PATH'] = offlineFlagSourcePath;
+    process.env['FLAGD_SERVICE_AUTHORITY'] = serviceAuthority;
 
     expect(getConfig()).toStrictEqual({
       host,
@@ -52,6 +54,7 @@ describe('Configuration', () => {
       resolverType,
       selector,
       offlineFlagSourcePath,
+      serviceAuthority,
     });
   });
 
@@ -64,6 +67,7 @@ describe('Configuration', () => {
       cache: 'lru',
       resolverType: 'rpc',
       selector: '',
+      serviceAuthority: '',
     };
 
     process.env['FLAGD_HOST'] = 'override';
diff --git a/libs/providers/flagd/src/lib/configuration.ts b/libs/providers/flagd/src/lib/configuration.ts
index cab759e40..b91bf8eb3 100644
--- a/libs/providers/flagd/src/lib/configuration.ts
+++ b/libs/providers/flagd/src/lib/configuration.ts
@@ -68,6 +68,13 @@ export interface Config {
    * @default 1000
    */
   maxCacheSize?: number;
+
+  /**
+   * The target host (authority) when routing requests through a proxy (e.g. Envoy)
+   *
+   * @default ''
+   */
+  serviceAuthority?: string;
 }
 
 export type FlagdProviderOptions = Partial<Config>;
@@ -94,6 +101,7 @@ enum ENV_VAR {
   FLAGD_SOURCE_SELECTOR = 'FLAGD_SOURCE_SELECTOR',
   FLAGD_RESOLVER = 'FLAGD_RESOLVER',
   FLAGD_OFFLINE_FLAG_SOURCE_PATH = 'FLAGD_OFFLINE_FLAG_SOURCE_PATH',
+  FLAGD_SERVICE_AUTHORITY = 'FLAGD_SERVICE_AUTHORITY',
 }
 
 const getEnvVarConfig = (): Partial<Config> => ({
@@ -124,6 +132,9 @@ const getEnvVarConfig = (): Partial<Config> => ({
   ...(process.env[ENV_VAR.FLAGD_OFFLINE_FLAG_SOURCE_PATH] && {
     offlineFlagSourcePath: process.env[ENV_VAR.FLAGD_OFFLINE_FLAG_SOURCE_PATH],
   }),
+  ...(process.env[ENV_VAR.FLAGD_SERVICE_AUTHORITY] && {
+    serviceAuthority: process.env[ENV_VAR.FLAGD_SERVICE_AUTHORITY],
+  }),
 });
 
 export function getConfig(options: FlagdProviderOptions = {}) {
diff --git a/libs/providers/flagd/src/lib/service/in-process/grpc/grpc-fetch.ts b/libs/providers/flagd/src/lib/service/in-process/grpc/grpc-fetch.ts
index fd791f72c..6b12dbfef 100644
--- a/libs/providers/flagd/src/lib/service/in-process/grpc/grpc-fetch.ts
+++ b/libs/providers/flagd/src/lib/service/in-process/grpc/grpc-fetch.ts
@@ -1,4 +1,4 @@
-import { ClientReadableStream, ServiceError, credentials } from '@grpc/grpc-js';
+import { ClientReadableStream, ServiceError, credentials, ClientOptions } from '@grpc/grpc-js';
 import { Logger } from '@openfeature/core';
 import { GeneralError } from '@openfeature/server-sdk';
 import { FlagSyncServiceClient, SyncFlagsRequest, SyncFlagsResponse } from '../../../../proto/ts/flagd/sync/v1/sync';
@@ -28,13 +28,21 @@ export class GrpcFetch implements DataFetch {
   private _isConnected = false;
 
   constructor(config: Config, syncServiceClient?: FlagSyncServiceClient, logger?: Logger) {
-    const { host, port, tls, socketPath, selector } = config;
+    const { host, port, tls, socketPath, selector, serviceAuthority } = config;
+
+    let clientOptions: ClientOptions | undefined;
+    if (serviceAuthority) {
+      clientOptions = {
+        'grpc.default_authority': serviceAuthority,
+      };
+    }
 
     this._syncClient = syncServiceClient
       ? syncServiceClient
       : new FlagSyncServiceClient(
           socketPath ? `unix://${socketPath}` : `${host}:${port}`,
           tls ? credentials.createSsl() : credentials.createInsecure(),
+          clientOptions,
         );
 
     this._logger = logger;