diff --git a/cryptography/hazmat/bindings/openssl/backend.py b/cryptography/hazmat/bindings/openssl/backend.py
index 0c3d22d..1cb886d 100644
--- a/cryptography/hazmat/bindings/openssl/backend.py
+++ b/cryptography/hazmat/bindings/openssl/backend.py
@@ -21,7 +21,7 @@
 from cryptography.exceptions import UnsupportedAlgorithm
 from cryptography.hazmat.primitives import interfaces
 from cryptography.hazmat.primitives.ciphers.algorithms import (
-    AES, Blowfish, Camellia, CAST5, TripleDES,
+    AES, Blowfish, Camellia, CAST5, TripleDES, ARC4,
 )
 from cryptography.hazmat.primitives.ciphers.modes import (
     CBC, CTR, ECB, OFB, CFB
@@ -254,6 +254,11 @@
             ECB,
             GetCipherByName("cast5-ecb")
         )
+        self.register_cipher_adapter(
+            ARC4,
+            type(None),
+            GetCipherByName("rc4")
+        )
 
     def create_encrypt_ctx(self, cipher, mode):
         return _CipherContext(self._backend, cipher, mode,
diff --git a/cryptography/hazmat/primitives/ciphers/algorithms.py b/cryptography/hazmat/primitives/ciphers/algorithms.py
index 8046bd2..cbfaceb 100644
--- a/cryptography/hazmat/primitives/ciphers/algorithms.py
+++ b/cryptography/hazmat/primitives/ciphers/algorithms.py
@@ -116,3 +116,22 @@
     @property
     def key_size(self):
         return len(self.key) * 8
+
+
+class ARC4(object):
+    name = "RC4"
+    key_sizes = frozenset([40, 56, 64, 80, 128, 192, 256])
+
+    def __init__(self, key):
+        super(ARC4, self).__init__()
+        self.key = key
+
+        # Verify that the key size matches the expected key size
+        if self.key_size not in self.key_sizes:
+            raise ValueError("Invalid key size ({0}) for {1}".format(
+                self.key_size, self.name
+            ))
+
+    @property
+    def key_size(self):
+        return len(self.key) * 8
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index 7d3b072..4d0703b 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -149,6 +149,16 @@
     :param bytes key: The secret key, 32-448 bits in length (in increments of
                       8).  This must be kept secret.
 
+.. class:: ARC4(key)
+
+    ARC4 (Alleged RC4) is a stream cipher with serious weaknesses in its
+    initial stream output. Its use is strongly discouraged. ARC4 does not use
+    mode constructions.
+
+    :param bytes key: The secret key, ``40``, ``56``, ``64``, ``80``, ``128``,
+                      ``192``, or ``256`` bits in length.  This must be kept
+                      secret.
+
 Modes
 ~~~~~
 
diff --git a/tests/hazmat/primitives/test_arc4.py b/tests/hazmat/primitives/test_arc4.py
new file mode 100644
index 0000000..cf0c5eb
--- /dev/null
+++ b/tests/hazmat/primitives/test_arc4.py
@@ -0,0 +1,43 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import absolute_import, division, print_function
+
+import binascii
+import os
+
+from cryptography.hazmat.primitives.ciphers import algorithms
+
+from .utils import generate_stream_encryption_test
+from ...utils import load_nist_vectors_from_file
+
+
+class TestARC4(object):
+    test_thing = generate_stream_encryption_test(
+        lambda path: load_nist_vectors_from_file(path, "ENCRYPT"),
+        os.path.join("ciphers", "ARC4"),
+        [
+            "rfc-6229-40.txt",
+            "rfc-6229-56.txt",
+            "rfc-6229-64.txt",
+            "rfc-6229-80.txt",
+            "rfc-6229-128.txt",
+            "rfc-6229-192.txt",
+            "rfc-6229-256.txt",
+        ],
+        lambda key: algorithms.ARC4(binascii.unhexlify((key))),
+        only_if=lambda backend: backend.ciphers.supported(
+            algorithms.ARC4("\x00" * 16), None
+        ),
+        skip_message="Does not support ARC4",
+    )
diff --git a/tests/hazmat/primitives/test_utils.py b/tests/hazmat/primitives/test_utils.py
index d7247e6..cee0b20 100644
--- a/tests/hazmat/primitives/test_utils.py
+++ b/tests/hazmat/primitives/test_utils.py
@@ -2,7 +2,7 @@
 
 from .utils import (
     base_hash_test, encrypt_test, hash_test, long_string_hash_test,
-    base_hmac_test, hmac_test
+    base_hmac_test, hmac_test, stream_encryption_test
 )
 
 
@@ -70,3 +70,14 @@
                 skip_message="message!"
             )
         assert exc_info.value.args[0] == "message!"
+
+
+class TestStreamEncryptionTest(object):
+    def test_skips_if_only_if_returns_false(self):
+        with pytest.raises(pytest.skip.Exception) as exc_info:
+            stream_encryption_test(
+                None, None, None,
+                only_if=lambda backend: False,
+                skip_message="message!"
+            )
+        assert exc_info.value.args[0] == "message!"
diff --git a/tests/hazmat/primitives/utils.py b/tests/hazmat/primitives/utils.py
index e6e97d1..90c15b1 100644
--- a/tests/hazmat/primitives/utils.py
+++ b/tests/hazmat/primitives/utils.py
@@ -49,6 +49,45 @@
     assert actual_plaintext == binascii.unhexlify(plaintext)
 
 
+def generate_stream_encryption_test(param_loader, path, file_names,
+                                    cipher_factory, only_if=None,
+                                    skip_message=None):
+    def test_stream_encryption(self):
+        for backend in _ALL_BACKENDS:
+            for file_name in file_names:
+                for params in param_loader(os.path.join(path, file_name)):
+                    yield (
+                        stream_encryption_test,
+                        backend,
+                        cipher_factory,
+                        params,
+                        only_if,
+                        skip_message
+                    )
+    return test_stream_encryption
+
+
+def stream_encryption_test(backend, cipher_factory, params, only_if,
+                           skip_message):
+    if not only_if(backend):
+        pytest.skip(skip_message)
+    plaintext = params.pop("plaintext")
+    ciphertext = params.pop("ciphertext")
+    offset = params.pop("offset")
+    cipher = Cipher(cipher_factory(**params), None, backend)
+    encryptor = cipher.encryptor()
+    # throw away offset bytes
+    encryptor.update(b"\x00" * int(offset))
+    actual_ciphertext = encryptor.update(binascii.unhexlify(plaintext))
+    actual_ciphertext += encryptor.finalize()
+    assert actual_ciphertext == binascii.unhexlify(ciphertext)
+    decryptor = cipher.decryptor()
+    decryptor.update(b"\x00" * int(offset))
+    actual_plaintext = decryptor.update(binascii.unhexlify(ciphertext))
+    actual_plaintext += decryptor.finalize()
+    assert actual_plaintext == binascii.unhexlify(plaintext)
+
+
 def generate_hash_test(param_loader, path, file_names, hash_cls,
                        only_if=None, skip_message=None):
     def test_hash(self):