diff --git a/docs/request-options.rst b/docs/request-options.rst
index a076cccae..bb99f82ae 100644
--- a/docs/request-options.rst
+++ b/docs/request-options.rst
@@ -162,6 +162,20 @@ digest
     creating a replacement that can be used with any HTTP handler is
     planned.
 
+ntlm
+    Use `Microsoft NTLM authentication <https://msdn.microsoft.com/en-us/library/windows/desktop/aa378749(v=vs.85).aspx>`_
+    (must be supported by the HTTP handler).
+
+.. code-block:: php
+
+    $client->request('GET', '/get', [
+        'auth' => ['username', 'password', 'ntlm']
+    ]);
+
+.. note::
+
+    This is currently only supported when using the cURL handler.
+
 
 body
 ----
diff --git a/src/Client.php b/src/Client.php
index dd8a0dcfa..de4df8a5c 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -352,6 +352,10 @@ private function applyOptions(RequestInterface $request, array &$options)
                     $options['curl'][CURLOPT_HTTPAUTH] = CURLAUTH_DIGEST;
                     $options['curl'][CURLOPT_USERPWD] = "$value[0]:$value[1]";
                     break;
+                case 'ntlm':
+                    $options['curl'][CURLOPT_HTTPAUTH] = CURLAUTH_NTLM;
+                    $options['curl'][CURLOPT_USERPWD] = "$value[0]:$value[1]";
+                    break;
             }
         }
 
diff --git a/src/Handler/StreamHandler.php b/src/Handler/StreamHandler.php
index be2ab9a1d..d36787ac5 100644
--- a/src/Handler/StreamHandler.php
+++ b/src/Handler/StreamHandler.php
@@ -301,6 +301,16 @@ private function createStream(RequestInterface $request, array $options)
             );
         }
 
+        // Microsoft NTLM authentication only supported with curl handler
+        if (isset($options['auth'])
+            && is_array($options['auth'])
+            && isset($options['auth'][2])
+            && 'ntlm' == $options['auth'][2]
+        ) {
+
+            throw new \InvalidArgumentException('Microsoft NTLM authentication only supported with curl handler');
+        }
+
         $context = $this->createResource(
             function () use ($context, $params) {
                 return stream_context_create($context, $params);
diff --git a/tests/ClientTest.php b/tests/ClientTest.php
index c25a76f59..771c43ecc 100644
--- a/tests/ClientTest.php
+++ b/tests/ClientTest.php
@@ -389,6 +389,18 @@ public function testAuthCanBeArrayForDigestAuth()
         ], $last['curl']);
     }
 
+    public function testAuthCanBeArrayForNtlmAuth()
+    {
+        $mock = new MockHandler([new Response()]);
+        $client = new Client(['handler' => $mock]);
+        $client->get('http://foo.com', ['auth' => ['a', 'b', 'ntlm']]);
+        $last = $mock->getLastOptions();
+        $this->assertEquals([
+            CURLOPT_HTTPAUTH => 8,
+            CURLOPT_USERPWD  => 'a:b'
+        ], $last['curl']);
+    }
+
     public function testAuthCanBeCustomType()
     {
         $mock = new MockHandler([new Response()]);