diff --git a/Chaos/Md5.hpp b/Chaos/Md5.hpp
new file mode 100644
index 0000000..e913828
--- /dev/null
+++ b/Chaos/Md5.hpp
@@ -0,0 +1,300 @@
+#ifndef CHAOS_MD5HASHER_HPP
+#define CHAOS_MD5HASHER_HPP
+
+#include <cstdint>
+#include <array>
+#include <string>
+
+namespace Chaos::Md5
+{
+
+struct Buffer
+{
+    uint32_t Regs_[4] = { 0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476 };
+};
+
+using Block = std::array<uint32_t, 16>;
+
+struct Algorithm
+{
+public:
+    static void UpdateBuffer(Buffer & buffer, const Block & block)
+    {
+        uint32_t a = buffer.Regs_[0];
+        uint32_t b = buffer.Regs_[1];
+        uint32_t c = buffer.Regs_[2];
+        uint32_t d = buffer.Regs_[3];
+
+        FF(a, b, c, d, block[ 0], 0xd76aa478,  7);
+        FF(d, a, b, c, block[ 1], 0xe8c7b756, 12);
+        FF(c, d, a, b, block[ 2], 0x242070db, 17);
+        FF(b, c, d, a, block[ 3], 0xc1bdceee, 22);
+        FF(a, b, c, d, block[ 4], 0xf57c0faf,  7);
+        FF(d, a, b, c, block[ 5], 0x4787c62a, 12);
+        FF(c, d, a, b, block[ 6], 0xa8304613, 17);
+        FF(b, c, d, a, block[ 7], 0xfd469501, 22);
+        FF(a, b, c, d, block[ 8], 0x698098d8,  7);
+        FF(d, a, b, c, block[ 9], 0x8b44f7af, 12);
+        FF(c, d, a, b, block[10], 0xffff5bb1, 17);
+        FF(b, c, d, a, block[11], 0x895cd7be, 22);
+        FF(a, b, c, d, block[12], 0x6b901122,  7);
+        FF(d, a, b, c, block[13], 0xfd987193, 12);
+        FF(c, d, a, b, block[14], 0xa679438e, 17);
+        FF(b, c, d, a, block[15], 0x49b40821, 22);
+
+        GG(a, b, c, d, block[ 1], 0xf61e2562,  5);
+        GG(d, a, b, c, block[ 6], 0xc040b340,  9);
+        GG(c, d, a, b, block[11], 0x265e5a51, 14);
+        GG(b, c, d, a, block[ 0], 0xe9b6c7aa, 20);
+        GG(a, b, c, d, block[ 5], 0xd62f105d,  5);
+        GG(d, a, b, c, block[10], 0x02441453,  9);
+        GG(c, d, a, b, block[15], 0xd8a1e681, 14);
+        GG(b, c, d, a, block[ 4], 0xe7d3fbc8, 20);
+        GG(a, b, c, d, block[ 9], 0x21e1cde6,  5);
+        GG(d, a, b, c, block[14], 0xc33707d6,  9);
+        GG(c, d, a, b, block[ 3], 0xf4d50d87, 14);
+        GG(b, c, d, a, block[ 8], 0x455a14ed, 20);
+        GG(a, b, c, d, block[13], 0xa9e3e905,  5);
+        GG(d, a, b, c, block[ 2], 0xfcefa3f8,  9);
+        GG(c, d, a, b, block[ 7], 0x676f02d9, 14);
+        GG(b, c, d, a, block[12], 0x8d2a4c8a, 20);
+
+        HH(a, b, c, d, block[ 5], 0xfffa3942,  4);
+        HH(d, a, b, c, block[ 8], 0x8771f681, 11);
+        HH(c, d, a, b, block[11], 0x6d9d6122, 16);
+        HH(b, c, d, a, block[14], 0xfde5380c, 23);
+        HH(a, b, c, d, block[ 1], 0xa4beea44,  4);
+        HH(d, a, b, c, block[ 4], 0x4bdecfa9, 11);
+        HH(c, d, a, b, block[ 7], 0xf6bb4b60, 16);
+        HH(b, c, d, a, block[10], 0xbebfbc70, 23);
+        HH(a, b, c, d, block[13], 0x289b7ec6,  4);
+        HH(d, a, b, c, block[ 0], 0xeaa127fa, 11);
+        HH(c, d, a, b, block[ 3], 0xd4ef3085, 16);
+        HH(b, c, d, a, block[ 6], 0x04881d05, 23);
+        HH(a, b, c, d, block[ 9], 0xd9d4d039,  4);
+        HH(d, a, b, c, block[12], 0xe6db99e5, 11);
+        HH(c, d, a, b, block[15], 0x1fa27cf8, 16);
+        HH(b, c, d, a, block[ 2], 0xc4ac5665, 23);
+
+        II(a, b, c, d, block[ 0], 0xf4292244,  6);
+        II(d, a, b, c, block[ 7], 0x432aff97, 10);
+        II(c, d, a, b, block[14], 0xab9423a7, 15);
+        II(b, c, d, a, block[ 5], 0xfc93a039, 21);
+        II(a, b, c, d, block[12], 0x655b59c3,  6);
+        II(d, a, b, c, block[ 3], 0x8f0ccc92, 10);
+        II(c, d, a, b, block[10], 0xffeff47d, 15);
+        II(b, c, d, a, block[ 1], 0x85845dd1, 21);
+        II(a, b, c, d, block[ 8], 0x6fa87e4f,  6);
+        II(d, a, b, c, block[15], 0xfe2ce6e0, 10);
+        II(c, d, a, b, block[ 6], 0xa3014314, 15);
+        II(b, c, d, a, block[13], 0x4e0811a1, 21);
+        II(a, b, c, d, block[ 4], 0xf7537e82,  6);
+        II(d, a, b, c, block[11], 0xbd3af235, 10);
+        II(c, d, a, b, block[ 2], 0x2ad7d2bb, 15);
+        II(b, c, d, a, block[ 9], 0xeb86d391, 21);
+
+        buffer.Regs_[0] += a;
+        buffer.Regs_[1] += b;
+        buffer.Regs_[2] += c;
+        buffer.Regs_[3] += d;
+    }
+
+private:
+    static uint32_t Rotl(uint32_t v, int_fast8_t s)
+    {
+        return (v << s) | (v >> (32 - s));
+    }
+
+    static uint32_t F(uint32_t x, uint32_t y, uint32_t z)
+    {
+        return (x & y) | ((~x) & z);
+    }
+
+    static uint32_t G(uint32_t x, uint32_t y, uint32_t z)
+    {
+        return (x & z) | (y & (~z));
+    }
+
+    static uint32_t H(uint32_t x, uint32_t y, uint32_t z)
+    {
+        return x ^ y ^ z;
+    }
+
+    static uint32_t I(uint32_t x, uint32_t y, uint32_t z)
+    {
+        return y ^ (x | (~z));
+    }
+
+    static void FF(uint32_t & a, uint32_t b, uint32_t c, uint32_t d,
+                   uint32_t x, uint32_t t, int_fast8_t s)
+    {
+        a = b + Rotl(a + F(b, c, d) + x + t, s);
+    }
+
+    static void GG(uint32_t & a, uint32_t b, uint32_t c, uint32_t d,
+                   uint32_t x, uint32_t t, int_fast8_t s)
+    {
+        a = b + Rotl(a + G(b, c, d) + x + t, s);
+    }
+
+    static void HH(uint32_t & a, uint32_t b, uint32_t c, uint32_t d,
+                   uint32_t x, uint32_t t, int_fast8_t s)
+    {
+        a = b + Rotl(a + H(b, c, d) + x + t, s);
+    }
+
+    static void II(uint32_t & a, uint32_t b, uint32_t c, uint32_t d,
+                   uint32_t x, uint32_t t, int_fast8_t s)
+    {
+        a = b + Rotl(a + I(b, c, d) + x + t, s);
+    }
+};
+
+struct Hash
+{
+    std::string ToHexString() const
+    {
+        char buf[33];
+
+        std::sprintf(buf,
+                     "%02x%02x%02x%02x%02x%02x%02x%02x"
+                     "%02x%02x%02x%02x%02x%02x%02x%02x",
+                      RawDigest[ 0], RawDigest[ 1], RawDigest[ 2], RawDigest[ 3],
+                      RawDigest[ 4], RawDigest[ 5], RawDigest[ 6], RawDigest[ 7],
+                      RawDigest[ 8], RawDigest[ 9], RawDigest[10], RawDigest[11],
+                      RawDigest[12], RawDigest[13], RawDigest[14], RawDigest[15]);
+
+        return std::string(buf, buf + 32);
+    }
+
+    std::array<uint8_t, 16> RawDigest;
+};
+
+class Hasher
+{
+public:
+    Hasher()
+        : BlockSize_(0)
+        , Word_(0)
+        , WordBytesPacked_(0)
+        , MessageSizeBytes_(0)
+    {
+        Block_.fill(0);
+    }
+
+    template<typename InputIt>
+    void Update(InputIt begin, InputIt end)
+    {
+        MessageSizeBytes_ += UpdateImpl(begin, end);
+    }
+
+    Hash Finish()
+    {
+        uint64_t messageSizeBytesMod64 = MessageSizeBytes_ % 64;
+
+        int_fast8_t paddingNeededBytes;
+
+        if (messageSizeBytesMod64 < 56)
+        {
+            paddingNeededBytes = 56 - messageSizeBytesMod64;
+        }
+        else if (messageSizeBytesMod64 > 56)
+        {
+            paddingNeededBytes = 120 - messageSizeBytesMod64;
+        }
+        else
+        {
+            paddingNeededBytes = 64;
+        }
+
+        UpdateImpl(PAD_, PAD_ + paddingNeededBytes);
+
+        const uint64_t messageSizeBits = MessageSizeBytes_ * 8;
+
+        uint8_t encodedMessageSizeBits[] =
+        {
+            static_cast<uint8_t>((messageSizeBits >>  0) & 0xFF),
+            static_cast<uint8_t>((messageSizeBits >>  8) & 0xFF),
+            static_cast<uint8_t>((messageSizeBits >> 16) & 0xFF),
+            static_cast<uint8_t>((messageSizeBits >> 24) & 0xFF),
+            static_cast<uint8_t>((messageSizeBits >> 32) & 0xFF),
+            static_cast<uint8_t>((messageSizeBits >> 40) & 0xFF),
+            static_cast<uint8_t>((messageSizeBits >> 48) & 0xFF),
+            static_cast<uint8_t>((messageSizeBits >> 56) & 0xFF),
+        };
+
+        static_assert(std::size(encodedMessageSizeBits) == 8);
+
+        UpdateImpl(encodedMessageSizeBits,
+                   encodedMessageSizeBits + std::size(encodedMessageSizeBits));
+
+        Hash result;
+
+        int_fast8_t i = 0;
+        for (int_fast8_t reg = 0; reg < 4; ++reg)
+        {
+            for (int_fast8_t shift = 0; shift < 32; shift += 8)
+            {
+                result.RawDigest[i++] = (Buffer_.Regs_[reg] >> shift) & 0xFF;
+            }
+        }
+
+        return result;
+    }
+
+private:
+    static constexpr uint8_t PAD_[] =
+    {
+        0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+    };
+
+    static_assert(std::size(PAD_) == 64);
+
+    Buffer Buffer_;
+
+    Block Block_;
+    int_fast8_t BlockSize_;
+
+    uint32_t Word_;
+    int_fast8_t WordBytesPacked_;
+
+    uint64_t MessageSizeBytes_;
+
+    template<typename InputIt>
+    uint64_t UpdateImpl(InputIt begin, InputIt end)
+    {
+        uint64_t written = 0;
+
+        for (InputIt it = begin; it != end; ++it, ++written)
+        {
+            Word_ |= (static_cast<uint32_t>(*it) << (WordBytesPacked_ * 8));
+            ++WordBytesPacked_;
+
+            if (WordBytesPacked_ == 4)
+            {
+                Block_[BlockSize_++] = Word_;
+                WordBytesPacked_ = 0;
+                Word_ = 0;
+
+                if (BlockSize_ == 16)
+                {
+                    Algorithm::UpdateBuffer(Buffer_, Block_);
+                    BlockSize_ = 0;
+                }
+            }
+        }
+
+        return written;
+    }
+};
+
+} // namespace Chaos::Md5
+
+#endif
diff --git a/ChaosTests/CMakeLists.txt b/ChaosTests/CMakeLists.txt
index 0891ef0..f784ea2 100644
--- a/ChaosTests/CMakeLists.txt
+++ b/ChaosTests/CMakeLists.txt
@@ -9,7 +9,7 @@ FetchContent_Declare(
 set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
 FetchContent_MakeAvailable(googletest)
 
-add_executable(ChaosTests Md4HasherTests.cpp)
+add_executable(ChaosTests Md4HasherTests.cpp Md5HasherTests.cpp)
 target_link_libraries(ChaosTests gtest gtest_main)
 target_include_directories(ChaosTests PRIVATE
     $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/Chaos>
diff --git a/ChaosTests/MD5HasherTests.cpp b/ChaosTests/MD5HasherTests.cpp
new file mode 100644
index 0000000..b5e3053
--- /dev/null
+++ b/ChaosTests/MD5HasherTests.cpp
@@ -0,0 +1,177 @@
+#include <gtest/gtest.h>
+
+#include "Md5.hpp"
+
+using namespace Chaos;
+
+TEST(Md5Tests, RFCTest)
+{
+    struct Helper
+    {
+        std::string operator()(const char * in) const
+        {
+            Md5::Hasher hasher;
+            hasher.Update(in, in + strlen(in));
+            return hasher.Finish().ToHexString();
+        }
+    };
+
+    Helper hash;
+
+    ASSERT_EQ("d41d8cd98f00b204e9800998ecf8427e", hash(""));
+    ASSERT_EQ("0cc175b9c0f1b6a831c399e269772661", hash("a"));
+    ASSERT_EQ("900150983cd24fb0d6963f7d28e17f72", hash("abc"));
+    ASSERT_EQ("f96b697d7cb7938d525a2f31aaf161d0", hash("message digest"));
+    ASSERT_EQ("c3fcd3d76192e4007dfb496cca67e13b", hash("abcdefghijklmnopqrstuvwxyz"));
+    ASSERT_EQ("d174ab98d277d9f5a5611c2c9f419d9f", hash("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"));
+    ASSERT_EQ("57edf4a22be3c955ac49da2e2107b67a", hash("12345678901234567890123456789012345678901234567890123456789012345678901234567890"));
+}
+
+TEST(Md5Tests, PartialUpdateTest)
+{
+    {
+        // "a"
+        Md5::Hasher hasher;
+
+        {
+            const char * in = "a";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        {
+            const char * in = "";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        ASSERT_EQ("0cc175b9c0f1b6a831c399e269772661", hasher.Finish().ToHexString());
+    }
+
+    {
+        // "abc"
+        Md5::Hasher hasher;
+
+        {
+            const char * in = "ab";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        {
+            const char * in = "c";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        ASSERT_EQ("900150983cd24fb0d6963f7d28e17f72", hasher.Finish().ToHexString());
+    }
+
+    {
+        // "message digest"
+        Md5::Hasher hasher;
+
+        {
+            const char * in = "me";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        {
+            const char * in = "ssage ";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        {
+            const char * in = "diges";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        {
+            const char * in = "t";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        ASSERT_EQ("f96b697d7cb7938d525a2f31aaf161d0", hasher.Finish().ToHexString());
+    }
+
+    {
+        // "12345678901234567890123456789012345678901234567890123456789012345678901234567890"
+        Md5::Hasher hasher;
+
+        {
+            const char * in = "12345678901234567890";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        {
+            const char * in = "12345678901234567890";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        {
+            const char * in = "12345678901234567890";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        {
+            const char * in = "12345678901234567890";
+            hasher.Update(in, in + strlen(in));
+        }
+
+        ASSERT_EQ("57edf4a22be3c955ac49da2e2107b67a", hasher.Finish().ToHexString());
+    }
+}
+
+TEST(Md5Tests, LongInputTest)
+{
+    struct Helper
+    {
+        std::string operator()(const char * in) const
+        {
+            Md5::Hasher hasher;
+            hasher.Update(in, in + strlen(in));
+            return hasher.Finish().ToHexString();
+        }
+    };
+
+    Helper hash;
+
+    // 2500 zeros ('0').
+    ASSERT_EQ("17aa376e13f65b7a4cb1a4913b5e748c", hash(std::string(2500, '0').c_str()));
+    // 1000 'a' followed by 1000 'b'.
+    ASSERT_EQ("5ede0802e614ef9cccc73dc02f04c032", hash((std::string(1000, 'a') +
+                                                        std::string(1000, 'b')).c_str()));
+}
+
+TEST(Md5Tests, LongInputPartialUpdateTest)
+{
+    {
+        // 2500 zeros ('0').
+        Md5::Hasher hasher;
+
+        std::string in(750, '0');
+
+        hasher.Update(in.begin(), in.begin() + 250);
+        hasher.Update(in.begin(), in.begin() + 500);
+        hasher.Update(in.begin(), in.begin() + 500);
+        hasher.Update(in.begin(), in.begin() + 750);
+        hasher.Update(in.begin(), in.begin() + 333);
+        hasher.Update(in.begin(), in.begin() + 167);
+
+        ASSERT_EQ("17aa376e13f65b7a4cb1a4913b5e748c", hasher.Finish().ToHexString());
+    }
+
+    {
+        // 1000 'a' followed by 1000 'b'.
+        Md5::Hasher hasher;
+
+        std::string inA(1000, 'a');
+        std::string inB(1000, 'b');
+
+        hasher.Update(inA.begin(), inA.begin() + 100);
+        hasher.Update(inA.begin(), inA.begin() + 255);
+        hasher.Update(inA.begin(), inA.begin() + 645);
+
+        hasher.Update(inB.begin(), inB.begin() + 33);
+        hasher.Update(inB.begin(), inB.begin() + 701);
+        hasher.Update(inB.begin(), inB.begin() + 266);
+
+        ASSERT_EQ("5ede0802e614ef9cccc73dc02f04c032", hasher.Finish().ToHexString());
+    }
+}