diff --git a/cng/rc4.go b/cng/rc4.go
new file mode 100644
index 0000000..e0d4507
--- /dev/null
+++ b/cng/rc4.go
@@ -0,0 +1,61 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+//go:build windows
+// +build windows
+
+package cng
+
+import (
+	"runtime"
+
+	"github.com/microsoft/go-crypto-winnative/internal/bcrypt"
+	"github.com/microsoft/go-crypto-winnative/internal/subtle"
+)
+
+// A RC4Cipher is an instance of RC4 using a particular key.
+type RC4Cipher struct {
+	kh bcrypt.KEY_HANDLE
+}
+
+// NewRC4Cipher creates and returns a new Cipher.
+func NewRC4Cipher(key []byte) (*RC4Cipher, error) {
+	kh, err := newCipherHandle(bcrypt.RC4_ALGORITHM, "", key)
+	if err != nil {
+		return nil, err
+	}
+	c := &RC4Cipher{kh: kh}
+	runtime.SetFinalizer(c, (*RC4Cipher).finalize)
+	return c, nil
+}
+
+func (c *RC4Cipher) finalize() {
+	if c.kh != 0 {
+		bcrypt.DestroyKey(c.kh)
+	}
+}
+
+// Reset zeros the key data and makes the Cipher unusable.
+func (c *RC4Cipher) Reset() {
+	bcrypt.DestroyKey(c.kh)
+	c.kh = 0
+}
+
+// XORKeyStream sets dst to the result of XORing src with the key stream.
+// Dst and src must overlap entirely or not at all.
+func (c *RC4Cipher) XORKeyStream(dst, src []byte) {
+	if c.kh == 0 || len(src) == 0 {
+		return
+	}
+	if subtle.InexactOverlap(dst[:len(src)], src) {
+		panic("crypto/rc4: invalid buffer overlap")
+	}
+	var outLen uint32
+	if err := bcrypt.Encrypt(c.kh, src, nil, nil, dst, &outLen, 0); err != nil {
+		panic("crypto/rc4: encryption failed: " + err.Error())
+	}
+	if int(outLen) != len(src) {
+		panic("crypto/rc4: src not fully XORed")
+	}
+	runtime.KeepAlive(c)
+}
diff --git a/cng/rc4_test.go b/cng/rc4_test.go
new file mode 100644
index 0000000..3920b15
--- /dev/null
+++ b/cng/rc4_test.go
@@ -0,0 +1,164 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+//go:build windows
+// +build windows
+
+package cng_test
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+
+	"github.com/microsoft/go-crypto-winnative/cng"
+)
+
+type rc4Test struct {
+	key, keystream []byte
+}
+
+var golden = []rc4Test{
+	// Test vectors from the original cypherpunk posting of ARC4:
+	//   https://groups.google.com/group/sci.crypt/msg/10a300c9d21afca0?pli=1
+	{
+		[]byte{0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef},
+		[]byte{0x74, 0x94, 0xc2, 0xe7, 0x10, 0x4b, 0x08, 0x79},
+	},
+	{
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{0xde, 0x18, 0x89, 0x41, 0xa3, 0x37, 0x5d, 0x3a},
+	},
+	{
+		[]byte{0xef, 0x01, 0x23, 0x45},
+		[]byte{0xd6, 0xa1, 0x41, 0xa7, 0xec, 0x3c, 0x38, 0xdf, 0xbd, 0x61},
+	},
+
+	// Test vectors from the Wikipedia page: https://en.wikipedia.org/wiki/RC4
+	{
+		[]byte{0x4b, 0x65, 0x79},
+		[]byte{0xeb, 0x9f, 0x77, 0x81, 0xb7, 0x34, 0xca, 0x72, 0xa7, 0x19},
+	},
+	{
+		[]byte{0x57, 0x69, 0x6b, 0x69},
+		[]byte{0x60, 0x44, 0xdb, 0x6d, 0x41, 0xb7},
+	},
+	{
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{
+			0xde, 0x18, 0x89, 0x41, 0xa3, 0x37, 0x5d, 0x3a,
+			0x8a, 0x06, 0x1e, 0x67, 0x57, 0x6e, 0x92, 0x6d,
+			0xc7, 0x1a, 0x7f, 0xa3, 0xf0, 0xcc, 0xeb, 0x97,
+			0x45, 0x2b, 0x4d, 0x32, 0x27, 0x96, 0x5f, 0x9e,
+			0xa8, 0xcc, 0x75, 0x07, 0x6d, 0x9f, 0xb9, 0xc5,
+			0x41, 0x7a, 0xa5, 0xcb, 0x30, 0xfc, 0x22, 0x19,
+			0x8b, 0x34, 0x98, 0x2d, 0xbb, 0x62, 0x9e, 0xc0,
+			0x4b, 0x4f, 0x8b, 0x05, 0xa0, 0x71, 0x08, 0x50,
+			0x92, 0xa0, 0xc3, 0x58, 0x4a, 0x48, 0xe4, 0xa3,
+			0x0a, 0x39, 0x7b, 0x8a, 0xcd, 0x1d, 0x00, 0x9e,
+			0xc8, 0x7d, 0x68, 0x11, 0xf2, 0x2c, 0xf4, 0x9c,
+			0xa3, 0xe5, 0x93, 0x54, 0xb9, 0x45, 0x15, 0x35,
+			0xa2, 0x18, 0x7a, 0x86, 0x42, 0x6c, 0xca, 0x7d,
+			0x5e, 0x82, 0x3e, 0xba, 0x00, 0x44, 0x12, 0x67,
+			0x12, 0x57, 0xb8, 0xd8, 0x60, 0xae, 0x4c, 0xbd,
+			0x4c, 0x49, 0x06, 0xbb, 0xc5, 0x35, 0xef, 0xe1,
+			0x58, 0x7f, 0x08, 0xdb, 0x33, 0x95, 0x5c, 0xdb,
+			0xcb, 0xad, 0x9b, 0x10, 0xf5, 0x3f, 0xc4, 0xe5,
+			0x2c, 0x59, 0x15, 0x65, 0x51, 0x84, 0x87, 0xfe,
+			0x08, 0x4d, 0x0e, 0x3f, 0x03, 0xde, 0xbc, 0xc9,
+			0xda, 0x1c, 0xe9, 0x0d, 0x08, 0x5c, 0x2d, 0x8a,
+			0x19, 0xd8, 0x37, 0x30, 0x86, 0x16, 0x36, 0x92,
+			0x14, 0x2b, 0xd8, 0xfc, 0x5d, 0x7a, 0x73, 0x49,
+			0x6a, 0x8e, 0x59, 0xee, 0x7e, 0xcf, 0x6b, 0x94,
+			0x06, 0x63, 0xf4, 0xa6, 0xbe, 0xe6, 0x5b, 0xd2,
+			0xc8, 0x5c, 0x46, 0x98, 0x6c, 0x1b, 0xef, 0x34,
+			0x90, 0xd3, 0x7b, 0x38, 0xda, 0x85, 0xd3, 0x2e,
+			0x97, 0x39, 0xcb, 0x23, 0x4a, 0x2b, 0xe7, 0x40,
+		},
+	},
+}
+
+func TestRC4Golden(t *testing.T) {
+	for gi, g := range golden {
+		data := make([]byte, len(g.keystream))
+		for i := range data {
+			data[i] = byte(i)
+		}
+
+		expect := make([]byte, len(g.keystream))
+		for i := range expect {
+			expect[i] = byte(i) ^ g.keystream[i]
+		}
+
+		for size := 1; size <= len(g.keystream); size++ {
+			c, err := cng.NewRC4Cipher(g.key)
+			if err != nil {
+				t.Fatalf("#%d: NewCipher: %v", gi, err)
+			}
+
+			off := 0
+			for off < len(g.keystream) {
+				n := len(g.keystream) - off
+				if n > size {
+					n = size
+				}
+				desc := fmt.Sprintf("#%d@[%d:%d]", gi, off, off+n)
+				src := data[off : off+n]
+				expect := expect[off : off+n]
+				dst := make([]byte, len(src))
+				c.XORKeyStream(dst, src)
+				for i, v := range dst {
+					if v != expect[i] {
+						t.Fatalf("%s: mismatch at byte %d:\nhave %x\nwant %x", desc, i, dst, expect)
+					}
+				}
+				off += n
+			}
+		}
+	}
+}
+
+func TestRC4Block(t *testing.T) {
+	c1a, _ := cng.NewRC4Cipher(golden[0].key)
+	c1b, _ := cng.NewRC4Cipher(golden[1].key)
+	data1 := make([]byte, 1<<20)
+	for i := range data1 {
+		c1a.XORKeyStream(data1[i:i+1], data1[i:i+1])
+		c1b.XORKeyStream(data1[i:i+1], data1[i:i+1])
+	}
+
+	c2a, _ := cng.NewRC4Cipher(golden[0].key)
+	c2b, _ := cng.NewRC4Cipher(golden[1].key)
+	data2 := make([]byte, 1<<20)
+	c2a.XORKeyStream(data2, data2)
+	c2b.XORKeyStream(data2, data2)
+
+	if !bytes.Equal(data1, data2) {
+		t.Fatalf("bad block")
+	}
+}
+
+func benchmarkRC4(b *testing.B, size int64) {
+	buf := make([]byte, size)
+	c, err := cng.NewRC4Cipher(golden[0].key)
+	if err != nil {
+		panic(err)
+	}
+	b.SetBytes(size)
+
+	for i := 0; i < b.N; i++ {
+		c.XORKeyStream(buf, buf)
+	}
+}
+
+func BenchmarkRC4_128(b *testing.B) {
+	benchmarkRC4(b, 128)
+}
+
+func BenchmarkRC4_1K(b *testing.B) {
+	benchmarkRC4(b, 1024)
+}
+
+func BenchmarkRC4_8K(b *testing.B) {
+	benchmarkRC4(b, 8096)
+}
diff --git a/internal/bcrypt/bcrypt_windows.go b/internal/bcrypt/bcrypt_windows.go
index 829ec66..37c64ba 100644
--- a/internal/bcrypt/bcrypt_windows.go
+++ b/internal/bcrypt/bcrypt_windows.go
@@ -19,6 +19,7 @@ const (
 	SHA3_384_ALGORITHM   = "SHA3-384"
 	SHA3_512_ALGORITHM   = "SHA3-512"
 	AES_ALGORITHM        = "AES"
+	RC4_ALGORITHM        = "RC4"
 	RSA_ALGORITHM        = "RSA"
 	MD4_ALGORITHM        = "MD4"
 	MD5_ALGORITHM        = "MD5"