diff --git a/requests/api.py b/requests/api.py
index b079eedd..3c79646b 100644
--- a/requests/api.py
+++ b/requests/api.py
@@ -33,6 +33,8 @@ def request(method, url, **kwargs):
     :param config: (optional) A configuration dictionary.
     :param verify: (optional) if ``True``, the SSL cert will be verified. A CA_BUNDLE path can also be provided.
     :param prefetch: (optional) if ``True``, the response content will be immediately downloaded.
+    :param key_file: (optional) ssl client key file.
+    :param cert_file: (optional) ssl client cert file.
     """
 
     s = kwargs.pop('session') if 'session' in kwargs else sessions.session()
diff --git a/requests/models.py b/requests/models.py
index 753e83ab..d827042b 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -63,7 +63,9 @@ class Request(object):
         config=None,
         _poolmanager=None,
         verify=None,
-        session=None):
+        session=None,
+        key_file=None,
+        cert_file=None):
 
         #: Dictionary of configurations for this request.
         self.config = dict(config or [])
@@ -143,6 +145,10 @@ class Request(object):
         #: SSL Verification.
         self.verify = verify
 
+        #: SSL Certificate
+        self.key_file = key_file
+        self.cert_file = cert_file
+
         if headers:
             headers = CaseInsensitiveDict(self.headers)
         else:
@@ -507,6 +513,10 @@ class Request(object):
             conn.cert_reqs = 'CERT_NONE'
             conn.ca_certs = None
 
+        if self.key_file and self.cert_file:
+            conn.key_file = self.key_file
+            conn.cert_file = self.cert_file
+
         if not self.sent or anyway:
 
             if self.cookies:
diff --git a/requests/sessions.py b/requests/sessions.py
index 04d7d5dd..90fbacf0 100644
--- a/requests/sessions.py
+++ b/requests/sessions.py
@@ -77,7 +77,9 @@ class Session(object):
         params=None,
         config=None,
         prefetch=False,
-        verify=True):
+        verify=True,
+        key_file=None,
+        cert_file=None):
 
         self.headers = headers or {}
         self.cookies = cookies or {}
@@ -89,6 +91,8 @@ class Session(object):
         self.config = config or {}
         self.prefetch = prefetch
         self.verify = verify
+        self.key_file = key_file
+        self.cert_file = cert_file
 
         for (k, v) in list(defaults.items()):
             self.config.setdefault(k, v)
@@ -131,7 +135,9 @@ class Session(object):
         return_response=True,
         config=None,
         prefetch=False,
-        verify=None):
+        verify=None,
+        key_file=None,
+        cert_file=None):
 
         """Constructs and sends a :class:`Request <Request>`.
         Returns :class:`Response <Response>` object.
@@ -188,6 +194,8 @@ class Session(object):
             proxies=proxies,
             config=config,
             verify=verify,
+            key_file=key_file,
+            cert_file=cert_file,
             _poolmanager=self.poolmanager
         )