diff --git a/cpp/include/ray/api.h b/cpp/include/ray/api.h
index e7ac0ffad792f..9261563c1fa90 100644
--- a/cpp/include/ray/api.h
+++ b/cpp/include/ray/api.h
@@ -111,8 +111,7 @@ ray::internal::ActorCreator<PyActorClass> Actor(PyActorClass func);
 ray::internal::ActorCreator<JavaActorClass> Actor(JavaActorClass func);
 
 /// Get a handle to a named actor in current namespace.
-/// Gets a handle to a named actor with the given name. The actor must have been created
-/// with name specified.
+/// The actor must have been created with name specified.
 ///
 /// \param[in] actor_name The name of the named actor.
 /// \return An ActorHandle to the actor if the actor of specified name exists or an
@@ -120,6 +119,17 @@ ray::internal::ActorCreator<JavaActorClass> Actor(JavaActorClass func);
 template <typename T>
 boost::optional<ActorHandle<T>> GetActor(const std::string &actor_name);
 
+/// Get a handle to a named actor in the given namespace.
+/// The actor must have been created with name specified.
+///
+/// \param[in] actor_name The name of the named actor.
+/// \param[in] namespace The namespace of the actor.
+/// \return An ActorHandle to the actor if the actor of specified name exists in
+/// specifiled namespace or an empty optional object.
+template <typename T>
+boost::optional<ActorHandle<T>> GetActor(const std::string &actor_name,
+                                         const std::string &ray_namespace);
+
 /// Intentionally exit the current actor.
 /// It is used to disconnect an actor and exit the worker.
 /// \Throws RayException if the current process is a driver or the current worker is not
@@ -271,11 +281,17 @@ inline ray::internal::ActorCreator<F> Actor(F create_func) {
 
 template <typename T>
 boost::optional<ActorHandle<T>> GetActor(const std::string &actor_name) {
+  return GetActor<T>(actor_name, "");
+}
+
+template <typename T>
+boost::optional<ActorHandle<T>> GetActor(const std::string &actor_name,
+                                         const std::string &ray_namespace) {
   if (actor_name.empty()) {
     return {};
   }
 
-  auto actor_id = ray::internal::GetRayRuntime()->GetActorId(actor_name);
+  auto actor_id = ray::internal::GetRayRuntime()->GetActorId(actor_name, ray_namespace);
   if (actor_id.empty()) {
     return {};
   }
diff --git a/cpp/include/ray/api/actor_creator.h b/cpp/include/ray/api/actor_creator.h
index 89742c345de39..feecfd20f40e3 100644
--- a/cpp/include/ray/api/actor_creator.h
+++ b/cpp/include/ray/api/actor_creator.h
@@ -39,6 +39,12 @@ class ActorCreator {
     return *this;
   }
 
+  ActorCreator &SetName(std::string name, std::string ray_namespace) {
+    create_options_.name = std::move(name);
+    create_options_.ray_namespace = std::move(ray_namespace);
+    return *this;
+  }
+
   ActorCreator &SetResources(std::unordered_map<std::string, double> resources) {
     create_options_.resources = std::move(resources);
     return *this;
diff --git a/cpp/include/ray/api/ray_config.h b/cpp/include/ray/api/ray_config.h
index ea187a65de3f4..5286b99c303f9 100644
--- a/cpp/include/ray/api/ray_config.h
+++ b/cpp/include/ray/api/ray_config.h
@@ -59,6 +59,9 @@ class RayConfig {
 
   // A specific flag for internal `default_worker`. Please don't use it in user code.
   bool is_worker_ = false;
+
+  // A namespace is a logical grouping of jobs and named actors.
+  std::string ray_namespace = "";
 };
 
 }  // namespace ray
diff --git a/cpp/include/ray/api/ray_runtime.h b/cpp/include/ray/api/ray_runtime.h
index ad29e792845e2..59f8ea6fbefce 100644
--- a/cpp/include/ray/api/ray_runtime.h
+++ b/cpp/include/ray/api/ray_runtime.h
@@ -78,7 +78,8 @@ class RayRuntime {
                                 const CallOptions &call_options) = 0;
   virtual void AddLocalReference(const std::string &id) = 0;
   virtual void RemoveLocalReference(const std::string &id) = 0;
-  virtual std::string GetActorId(const std::string &actor_name) = 0;
+  virtual std::string GetActorId(const std::string &actor_name,
+                                 const std::string &ray_namespace) = 0;
   virtual void KillActor(const std::string &str_actor_id, bool no_restart) = 0;
   virtual void ExitActor() = 0;
   virtual ray::PlacementGroup CreatePlacementGroup(
diff --git a/cpp/include/ray/api/task_options.h b/cpp/include/ray/api/task_options.h
index 5bae8abcaad00..8bdbf8327f5c0 100644
--- a/cpp/include/ray/api/task_options.h
+++ b/cpp/include/ray/api/task_options.h
@@ -99,6 +99,7 @@ struct CallOptions {
 
 struct ActorCreationOptions {
   std::string name;
+  std::string ray_namespace;
   std::unordered_map<std::string, double> resources;
   int max_restarts = 0;
   int max_concurrency = 1;
diff --git a/cpp/src/ray/config_internal.cc b/cpp/src/ray/config_internal.cc
index de43092c0cfd6..8a8f3e9703e95 100644
--- a/cpp/src/ray/config_internal.cc
+++ b/cpp/src/ray/config_internal.cc
@@ -186,6 +186,10 @@ void ConfigInternal::Init(RayConfig &config, int argc, char **argv) {
       code_search_path = absolute_path;
     }
   }
+  if (worker_type == WorkerType::DRIVER) {
+    ray_namespace =
+        config.ray_namespace.empty() ? GenerateUUIDV4() : config.ray_namespace;
+  }
 };
 
 void ConfigInternal::SetBootstrapAddress(std::string_view address) {
diff --git a/cpp/src/ray/config_internal.h b/cpp/src/ray/config_internal.h
index 8e24a72533762..d3c15be90b3c1 100644
--- a/cpp/src/ray/config_internal.h
+++ b/cpp/src/ray/config_internal.h
@@ -64,6 +64,8 @@ class ConfigInternal {
   rpc::JobConfig_ActorLifetime default_actor_lifetime =
       rpc::JobConfig_ActorLifetime_NON_DETACHED;
 
+  std::string ray_namespace = "";
+
   static ConfigInternal &Instance() {
     static ConfigInternal config;
     return config;
diff --git a/cpp/src/ray/runtime/abstract_ray_runtime.cc b/cpp/src/ray/runtime/abstract_ray_runtime.cc
index 7596c79dbfabf..73af3afefb9ca 100644
--- a/cpp/src/ray/runtime/abstract_ray_runtime.cc
+++ b/cpp/src/ray/runtime/abstract_ray_runtime.cc
@@ -242,8 +242,9 @@ void AbstractRayRuntime::RemoveLocalReference(const std::string &id) {
   }
 }
 
-std::string AbstractRayRuntime::GetActorId(const std::string &actor_name) {
-  auto actor_id = task_submitter_->GetActor(actor_name);
+std::string AbstractRayRuntime::GetActorId(const std::string &actor_name,
+                                           const std::string &ray_namespace) {
+  auto actor_id = task_submitter_->GetActor(actor_name, ray_namespace);
   if (actor_id.IsNil()) {
     return "";
   }
@@ -350,7 +351,9 @@ PlacementGroup AbstractRayRuntime::GetPlacementGroupById(const std::string &id)
 }
 
 PlacementGroup AbstractRayRuntime::GetPlacementGroup(const std::string &name) {
-  auto str_ptr = global_state_accessor_->GetPlacementGroupByName(name, "");
+  // TODO(WangTaoTheTonic): Add namespace support for placement group.
+  auto str_ptr = global_state_accessor_->GetPlacementGroupByName(
+      name, CoreWorkerProcess::GetCoreWorker().GetJobConfig().ray_namespace());
   if (str_ptr == nullptr) {
     return {};
   }
diff --git a/cpp/src/ray/runtime/abstract_ray_runtime.h b/cpp/src/ray/runtime/abstract_ray_runtime.h
index 12b061fdc7324..63e0d5fa75735 100644
--- a/cpp/src/ray/runtime/abstract_ray_runtime.h
+++ b/cpp/src/ray/runtime/abstract_ray_runtime.h
@@ -75,7 +75,7 @@ class AbstractRayRuntime : public RayRuntime {
 
   void RemoveLocalReference(const std::string &id);
 
-  std::string GetActorId(const std::string &actor_name);
+  std::string GetActorId(const std::string &actor_name, const std::string &ray_namespace);
 
   void KillActor(const std::string &str_actor_id, bool no_restart);
 
diff --git a/cpp/src/ray/runtime/task/local_mode_task_submitter.cc b/cpp/src/ray/runtime/task/local_mode_task_submitter.cc
index 5e3718d17e1ba..c62765d53b10b 100644
--- a/cpp/src/ray/runtime/task/local_mode_task_submitter.cc
+++ b/cpp/src/ray/runtime/task/local_mode_task_submitter.cc
@@ -145,7 +145,8 @@ ObjectID LocalModeTaskSubmitter::SubmitActorTask(InvocationSpec &invocation,
   return Submit(invocation, {});
 }
 
-ActorID LocalModeTaskSubmitter::GetActor(const std::string &actor_name) const {
+ActorID LocalModeTaskSubmitter::GetActor(const std::string &actor_name,
+                                         const std::string &ray_namespace) const {
   absl::MutexLock lock(&named_actors_mutex_);
   auto it = named_actors_.find(actor_name);
   if (it == named_actors_.end()) {
diff --git a/cpp/src/ray/runtime/task/local_mode_task_submitter.h b/cpp/src/ray/runtime/task/local_mode_task_submitter.h
index d79b76ea67a16..010a9d9c2369e 100644
--- a/cpp/src/ray/runtime/task/local_mode_task_submitter.h
+++ b/cpp/src/ray/runtime/task/local_mode_task_submitter.h
@@ -38,7 +38,7 @@ class LocalModeTaskSubmitter : public TaskSubmitter {
 
   ObjectID SubmitActorTask(InvocationSpec &invocation, const CallOptions &call_options);
 
-  ActorID GetActor(const std::string &actor_name) const;
+  ActorID GetActor(const std::string &actor_name, const std::string &ray_namespace) const;
 
   ray::PlacementGroup CreatePlacementGroup(
       const ray::PlacementGroupCreationOptions &create_options);
diff --git a/cpp/src/ray/runtime/task/native_task_submitter.cc b/cpp/src/ray/runtime/task/native_task_submitter.cc
index eb5d7632c3176..41521b896e10c 100644
--- a/cpp/src/ray/runtime/task/native_task_submitter.cc
+++ b/cpp/src/ray/runtime/task/native_task_submitter.cc
@@ -108,7 +108,7 @@ ActorID NativeTaskSubmitter::CreateActor(InvocationSpec &invocation,
   auto &core_worker = CoreWorkerProcess::GetCoreWorker();
   std::unordered_map<std::string, double> resources;
   std::string name = create_options.name;
-  std::string ray_namespace = "";
+  std::string ray_namespace = create_options.ray_namespace;
   BundleID bundle_id = GetBundleID(create_options);
   rpc::SchedulingStrategy scheduling_strategy;
   scheduling_strategy.mutable_default_scheduling_strategy();
@@ -145,9 +145,12 @@ ObjectID NativeTaskSubmitter::SubmitActorTask(InvocationSpec &invocation,
   return Submit(invocation, task_options);
 }
 
-ActorID NativeTaskSubmitter::GetActor(const std::string &actor_name) const {
+ActorID NativeTaskSubmitter::GetActor(const std::string &actor_name,
+                                      const std::string &ray_namespace) const {
   auto &core_worker = CoreWorkerProcess::GetCoreWorker();
-  auto pair = core_worker.GetNamedActorHandle(actor_name, "");
+  const std::string ns =
+      ray_namespace.empty() ? core_worker.GetJobConfig().ray_namespace() : ray_namespace;
+  auto pair = core_worker.GetNamedActorHandle(actor_name, ns);
   if (!pair.second.ok()) {
     RAY_LOG(WARNING) << pair.second.message();
     return ActorID::Nil();
diff --git a/cpp/src/ray/runtime/task/native_task_submitter.h b/cpp/src/ray/runtime/task/native_task_submitter.h
index 5beb5bbe54f40..6b71e6b329932 100644
--- a/cpp/src/ray/runtime/task/native_task_submitter.h
+++ b/cpp/src/ray/runtime/task/native_task_submitter.h
@@ -30,7 +30,7 @@ class NativeTaskSubmitter : public TaskSubmitter {
 
   ObjectID SubmitActorTask(InvocationSpec &invocation, const CallOptions &call_options);
 
-  ActorID GetActor(const std::string &actor_name) const;
+  ActorID GetActor(const std::string &actor_name, const std::string &ray_namespace) const;
 
   ray::PlacementGroup CreatePlacementGroup(
       const ray::PlacementGroupCreationOptions &create_options);
diff --git a/cpp/src/ray/runtime/task/task_submitter.h b/cpp/src/ray/runtime/task/task_submitter.h
index 567140886b766..5694aedc5cab1 100644
--- a/cpp/src/ray/runtime/task/task_submitter.h
+++ b/cpp/src/ray/runtime/task/task_submitter.h
@@ -38,7 +38,8 @@ class TaskSubmitter {
   virtual ObjectID SubmitActorTask(InvocationSpec &invocation,
                                    const CallOptions &call_options) = 0;
 
-  virtual ActorID GetActor(const std::string &actor_name) const = 0;
+  virtual ActorID GetActor(const std::string &actor_name,
+                           const std::string &ray_namespace) const = 0;
 
   virtual ray::PlacementGroup CreatePlacementGroup(
       const ray::PlacementGroupCreationOptions &create_options) = 0;
diff --git a/cpp/src/ray/test/cluster/cluster_mode_test.cc b/cpp/src/ray/test/cluster/cluster_mode_test.cc
index 7fec0be0cae3b..a696549b3984d 100644
--- a/cpp/src/ray/test/cluster/cluster_mode_test.cc
+++ b/cpp/src/ray/test/cluster/cluster_mode_test.cc
@@ -479,6 +479,41 @@ TEST(RayClusterModeTest, TaskWithPlacementGroup) {
   ray::RemovePlacementGroup(placement_group.GetID());
 }
 
+TEST(RayClusterModeTest, NamespaceTest) {
+  // Create a named actor in namespace `isolated_ns`.
+  std::string actor_name_in_isolated_ns = "named_actor_in_isolated_ns";
+  std::string isolated_ns_name = "isolated_ns";
+  ray::ActorHandle<Counter> actor =
+      ray::Actor(RAY_FUNC(Counter::FactoryCreate))
+          .SetName(actor_name_in_isolated_ns, isolated_ns_name)
+          .Remote();
+  auto initialized_obj = actor.Task(&Counter::Initialized).Remote();
+  EXPECT_TRUE(*initialized_obj.Get());
+  // It is invisible to job default namespace.
+  auto actor_optional = ray::GetActor<Counter>(actor_name_in_isolated_ns);
+  EXPECT_TRUE(!actor_optional);
+  // It is visible to the namespace it belongs.
+  actor_optional = ray::GetActor<Counter>(actor_name_in_isolated_ns, isolated_ns_name);
+  EXPECT_TRUE(actor_optional);
+  // It is invisible to any other namespaces.
+  actor_optional = ray::GetActor<Counter>(actor_name_in_isolated_ns, "other_ns");
+  EXPECT_TRUE(!actor_optional);
+
+  // Create a named actor in job default namespace.
+  std::string actor_name_in_default_ns = "actor_name_in_default_ns";
+  actor = ray::Actor(RAY_FUNC(Counter::FactoryCreate))
+              .SetName(actor_name_in_default_ns)
+              .Remote();
+  initialized_obj = actor.Task(&Counter::Initialized).Remote();
+  EXPECT_TRUE(*initialized_obj.Get());
+  // It is visible to job default namespace.
+  actor_optional = ray::GetActor<Counter>(actor_name_in_default_ns);
+  EXPECT_TRUE(actor_optional);
+  // It is invisible to any other namespaces.
+  actor_optional = ray::GetActor<Counter>(actor_name_in_default_ns, isolated_ns_name);
+  EXPECT_TRUE(!actor_optional);
+}
+
 int main(int argc, char **argv) {
   absl::ParseCommandLine(argc, argv);
   cmd_argc = argc;
diff --git a/cpp/src/ray/util/process_helper.cc b/cpp/src/ray/util/process_helper.cc
index ad3d34b966dcb..d684c67b4ba9d 100644
--- a/cpp/src/ray/util/process_helper.cc
+++ b/cpp/src/ray/util/process_helper.cc
@@ -151,6 +151,7 @@ void ProcessHelper::RayStart(CoreWorkerOptions::TaskExecutionCallback callback)
   for (const auto &path : ConfigInternal::Instance().code_search_path) {
     job_config.add_code_search_path(path);
   }
+  job_config.set_ray_namespace(ConfigInternal::Instance().ray_namespace);
   std::string serialized_job_config;
   RAY_CHECK(job_config.SerializeToString(&serialized_job_config));
   options.serialized_job_config = serialized_job_config;
diff --git a/python/ray/_private/worker.py b/python/ray/_private/worker.py
index 97977d280799d..d968d9c1436cf 100644
--- a/python/ray/_private/worker.py
+++ b/python/ray/_private/worker.py
@@ -1107,7 +1107,7 @@ def init(
             is true.
         log_to_driver: If true, the output from all of the worker
             processes on all nodes will be directed to the driver.
-        namespace: Namespace to use
+        namespace: A namespace is a logical grouping of jobs and named actors.
         runtime_env: The runtime environment to use
             for this job (see :ref:`runtime-environments` for details).
         storage: [Experimental] Specify a URI for persistent cluster-wide storage.
diff --git a/src/ray/util/util.h b/src/ray/util/util.h
index 7cd8650c19756..78c534e62d857 100644
--- a/src/ray/util/util.h
+++ b/src/ray/util/util.h
@@ -117,6 +117,38 @@ inline int64_t current_sys_time_us() {
   return mu_since_epoch.count();
 }
 
+inline std::string GenerateUUIDV4() {
+  static std::random_device rd;
+  static std::mt19937 gen(rd());
+  static std::uniform_int_distribution<> dis(0, 15);
+  static std::uniform_int_distribution<> dis2(8, 11);
+
+  std::stringstream ss;
+  int i;
+  ss << std::hex;
+  for (i = 0; i < 8; i++) {
+    ss << dis(gen);
+  }
+  ss << "-";
+  for (i = 0; i < 4; i++) {
+    ss << dis(gen);
+  }
+  ss << "-4";
+  for (i = 0; i < 3; i++) {
+    ss << dis(gen);
+  }
+  ss << "-";
+  ss << dis2(gen);
+  for (i = 0; i < 3; i++) {
+    ss << dis(gen);
+  }
+  ss << "-";
+  for (i = 0; i < 12; i++) {
+    ss << dis(gen);
+  };
+  return ss.str();
+}
+
 /// A helper function to parse command-line arguments in a platform-compatible manner.
 ///
 /// \param cmdline The command-line to split.