diff --git a/requests/api.py b/requests/api.py
index b079eedd..3188a2d0 100644
--- a/requests/api.py
+++ b/requests/api.py
@@ -33,6 +33,7 @@ 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 cert: (optional) if String, path to ssl client cert file (.pem). If Tuple, ('cert', 'key') pair.
     """
 
     s = kwargs.pop('session') if 'session' in kwargs else sessions.session()
diff --git a/requests/models.py b/requests/models.py
index 753e83ab..717e36fd 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -63,7 +63,8 @@ class Request(object):
         config=None,
         _poolmanager=None,
         verify=None,
-        session=None):
+        session=None,
+        cert=None):
 
         #: Dictionary of configurations for this request.
         self.config = dict(config or [])
@@ -143,6 +144,9 @@ class Request(object):
         #: SSL Verification.
         self.verify = verify
 
+        #: SSL Certificate
+        self.cert = cert
+
         if headers:
             headers = CaseInsensitiveDict(self.headers)
         else:
@@ -267,7 +271,8 @@ class Request(object):
                     _poolmanager=self._poolmanager,
                     proxies=self.proxies,
                     verify=self.verify,
-                    session=self.session
+                    session=self.session,
+                    cert=self.cert
                 )
 
                 request.send()
@@ -507,6 +512,13 @@ class Request(object):
             conn.cert_reqs = 'CERT_NONE'
             conn.ca_certs = None
 
+        if self.cert:
+            if type(self.cert) is tuple:
+                conn.cert_file = self.cert[0]
+                conn.key_file = self.cert[1]
+            else:
+                conn.cert_file = self.cert
+
         if not self.sent or anyway:
 
             if self.cookies:
diff --git a/requests/sessions.py b/requests/sessions.py
index 87320d6e..f66529e8 100644
--- a/requests/sessions.py
+++ b/requests/sessions.py
@@ -52,7 +52,7 @@ class Session(object):
 
     __attrs__ = [
         'headers', 'cookies', 'auth', 'timeout', 'proxies', 'hooks',
-        'params', 'config', 'verify']
+        'params', 'config', 'verify', 'cert']
 
 
     def __init__(self,
@@ -65,7 +65,8 @@ class Session(object):
         params=None,
         config=None,
         prefetch=False,
-        verify=True):
+        verify=True,
+        cert=None):
 
         self.headers = headers or {}
         self.cookies = cookies or {}
@@ -77,6 +78,7 @@ class Session(object):
         self.config = config or {}
         self.prefetch = prefetch
         self.verify = verify
+        self.cert = cert
 
         for (k, v) in list(defaults.items()):
             self.config.setdefault(k, v)
@@ -119,7 +121,8 @@ class Session(object):
         return_response=True,
         config=None,
         prefetch=False,
-        verify=None):
+        verify=None,
+        cert=None):
 
         """Constructs and sends a :class:`Request <Request>`.
         Returns :class:`Response <Response>` object.
@@ -139,6 +142,7 @@ class Session(object):
         :param config: (optional) A configuration dictionary.
         :param prefetch: (optional) if ``True``, the response content will be immediately downloaded.
         :param verify: (optional) if ``True``, the SSL cert will be verified. A CA_BUNDLE path can also be provided.
+        :param cert: (optional) if String, path to ssl client cert file (.pem). If Tuple, ('cert', 'key') pair.
         """
 
         method = str(method).upper()
@@ -176,6 +180,7 @@ class Session(object):
             proxies=proxies,
             config=config,
             verify=verify,
+            cert=cert,
             _poolmanager=self.poolmanager
         )