diff --git a/c/src/point_one/polaris/polaris.c b/c/src/point_one/polaris/polaris.c
index 017be59..2e69a6c 100644
--- a/c/src/point_one/polaris/polaris.c
+++ b/c/src/point_one/polaris/polaris.c
@@ -177,6 +177,12 @@ void Polaris_SetLogLevel(int log_level) {
 /******************************************************************************/
 int Polaris_Authenticate(PolarisContext_t* context, const char* api_key,
                          const char* unique_id) {
+  return Polaris_AuthenticateTo(context, api_key, unique_id, POLARIS_API_URL);
+}
+
+/******************************************************************************/
+int Polaris_AuthenticateTo(PolarisContext_t* context, const char* api_key,
+                           const char* unique_id, const char* api_url) {
   // Sanity check the inputs.
   if (strlen(api_key) == 0) {
     P1_Print("API key must not be empty.\n");
@@ -210,16 +216,16 @@ int Polaris_Authenticate(PolarisContext_t* context, const char* api_key,
     return POLARIS_NOT_ENOUGH_SPACE;
   }
 
-  P1_DebugPrint("Sending auth request. [api_key=%s, unique_id=%s]\n", api_key,
-             unique_id);
+  P1_DebugPrint("Sending auth request. [api_key=%s, unique_id=%s, url=%s]\n",
+                api_key, unique_id, api_url);
   context->auth_token[0] = '\0';
 #ifdef POLARIS_USE_TLS
   int status_code =
-      SendPOSTRequest(context, POLARIS_API_URL, 443, "/api/v1/auth/token",
+      SendPOSTRequest(context, api_url, 443, "/api/v1/auth/token",
                       context->recv_buffer, (size_t)content_size);
 #else
   int status_code =
-      SendPOSTRequest(context, POLARIS_API_URL, 80, "/api/v1/auth/token",
+      SendPOSTRequest(context, api_url, 80, "/api/v1/auth/token",
                       context->recv_buffer, (size_t)content_size);
 #endif
   if (status_code < 0) {
diff --git a/c/src/point_one/polaris/polaris.h b/c/src/point_one/polaris/polaris.h
index ac0c76c..92cc030 100644
--- a/c/src/point_one/polaris/polaris.h
+++ b/c/src/point_one/polaris/polaris.h
@@ -10,6 +10,8 @@
 
 #include "point_one/polaris/socket.h"
 
+#define POLARIS_API_URL "api.pointonenav.com"
+
 #define POLARIS_ENDPOINT_URL "polaris.pointonenav.com"
 #define POLARIS_ENDPOINT_PORT 8088
 #define POLARIS_ENDPOINT_TLS_PORT 8090
@@ -203,6 +205,16 @@ void Polaris_SetLogLevel(int log_level);
 int Polaris_Authenticate(PolarisContext_t* context, const char* api_key,
                          const char* unique_id);
 
+/**
+ * @brief Authenticate with the specified Polaris API server.
+ *
+ * @copydetails Polaris_Authenticate()
+ *
+ * @param api_url The URL of the desired API authentication server.
+ */
+int Polaris_AuthenticateTo(PolarisContext_t* context, const char* api_key,
+                           const char* unique_id, const char* api_url);
+
 /**
  * @brief Use an existing authentication token to connect to Polaris.
  *
diff --git a/c/src/point_one/polaris/polaris_internal.h b/c/src/point_one/polaris/polaris_internal.h
index 02ca881..c6f4aaf 100644
--- a/c/src/point_one/polaris/polaris_internal.h
+++ b/c/src/point_one/polaris/polaris_internal.h
@@ -23,8 +23,6 @@
 #define POLARIS_ID_BEACON 0x05
 #define POLARIS_ID_UNIQUE_ID 0x06
 
-#define POLARIS_API_URL "api.pointonenav.com"
-
 // Enforce 4-byte alignment and packing of all data structures and values so
 // that values larger than 1 B are aligned on platforms that require it.
 #pragma pack(push, 4)
diff --git a/src/point_one/polaris/polaris_client.cc b/src/point_one/polaris/polaris_client.cc
index 30ea4ee..6b97071 100644
--- a/src/point_one/polaris/polaris_client.cc
+++ b/src/point_one/polaris/polaris_client.cc
@@ -68,6 +68,7 @@ PolarisClient::PolarisClient(const std::string& api_key,
     Polaris_SetLogLevel(POLARIS_LOG_LEVEL_TRACE);
   }
 
+  SetPolarisAuthenticationServer();
   SetPolarisEndpoint();
 
   polaris_.SetRTCMCallback([&](const uint8_t* buffer, size_t size_bytes) {
@@ -114,6 +115,17 @@ void PolarisClient::SetNoAuthID(const std::string& unique_id) {
   no_auth_ = true;
 }
 
+/******************************************************************************/
+void PolarisClient::SetPolarisAuthenticationServer(const std::string& api_url) {
+  std::unique_lock<std::recursive_mutex> lock(mutex_);
+  if (api_url.empty()) {
+    api_url_ = POLARIS_API_URL;
+  }
+  else {
+    api_url_ = api_url;
+  }
+}
+
 /******************************************************************************/
 void PolarisClient::SetPolarisEndpoint(const std::string& endpoint_url,
                                        int endpoint_port) {
@@ -200,8 +212,9 @@ void PolarisClient::Run(double timeout_sec) {
     // Retrieve an access token using the specified API key.
     if (!auth_valid_ && !no_auth_) {
       VLOG(1) << "Authenticating with Polaris service. [unique_id="
-              << (unique_id_.empty() ? "<not specified>" : unique_id_) << "]";
-      int ret = polaris_.Authenticate(api_key_, unique_id_);
+              << (unique_id_.empty() ? "<not specified>" : unique_id_)
+              << ", api_url=" << api_url_ << "]";
+      int ret = polaris_.AuthenticateTo(api_key_, unique_id_, api_url_);
       if (ret == POLARIS_FORBIDDEN) {
         LOG(ERROR) << "Authentication rejected. Is your API key valid?";
         running_ = false;
diff --git a/src/point_one/polaris/polaris_client.h b/src/point_one/polaris/polaris_client.h
index b4205ca..ba3a339 100644
--- a/src/point_one/polaris/polaris_client.h
+++ b/src/point_one/polaris/polaris_client.h
@@ -124,6 +124,14 @@ class PolarisClient {
    */
   void SetNoAuthID(const std::string& unique_id);
 
+  /**
+   * @brief Specify an alternate URL to use when authenticating with the Polaris
+   *        corrections service.
+   *
+   * @param api_url The desired endpoint URL.
+   */
+  void SetPolarisAuthenticationServer(const std::string& api_url = "");
+
   /**
    * @brief Specify an alternate URL to use when connecting to the Polaris
    *        corrections endpoint.
@@ -252,6 +260,8 @@ class PolarisClient {
 
   std::function<void(const uint8_t* buffer, size_t size_bytes)> callback_;
 
+  std::string api_url_;
+
   std::string endpoint_url_;
   int endpoint_port_ = 0;
 
diff --git a/src/point_one/polaris/polaris_interface.cc b/src/point_one/polaris/polaris_interface.cc
index 8d39c61..e53fd38 100644
--- a/src/point_one/polaris/polaris_interface.cc
+++ b/src/point_one/polaris/polaris_interface.cc
@@ -26,6 +26,14 @@ int PolarisInterface::Authenticate(const std::string& api_key,
   return Polaris_Authenticate(&context_, api_key.c_str(), unique_id.c_str());
 }
 
+/******************************************************************************/
+int PolarisInterface::AuthenticateTo(const std::string& api_key,
+                                     const std::string& unique_id,
+                                     const std::string& api_url) {
+  return Polaris_AuthenticateTo(&context_, api_key.c_str(), unique_id.c_str(),
+                                api_url.c_str());
+}
+
 /******************************************************************************/
 int PolarisInterface::SetAuthToken(const std::string& auth_token) {
   return Polaris_SetAuthToken(&context_, auth_token.c_str());
diff --git a/src/point_one/polaris/polaris_interface.h b/src/point_one/polaris/polaris_interface.h
index c53e1d0..71ef6f2 100644
--- a/src/point_one/polaris/polaris_interface.h
+++ b/src/point_one/polaris/polaris_interface.h
@@ -73,6 +73,18 @@ class PolarisInterface {
    */
   int Authenticate(const std::string& api_key, const std::string& unique_id);
 
+  /**
+    * @brief Authenticate with the specified Polaris API server.
+   *
+   * @copydetails Authenticate()
+   *
+   * See also @ref Polaris_AuthenticateTo().
+   *
+   * @param api_url The URL of the desired API authentication server.
+   */
+  int AuthenticateTo(const std::string& api_key, const std::string& unique_id,
+                     const std::string& api_url);
+
   /**
    * @brief Use an existing authentication token to connect to Polaris.
    *