diff --git a/spec/std/uuid_spec.cr b/spec/std/uuid_spec.cr
new file mode 100644
index 000000000000..fdd4bb4e2878
--- /dev/null
+++ b/spec/std/uuid_spec.cr
@@ -0,0 +1,84 @@
+require "spec"
+require "uuid"
+
+describe "UUID" do
+  it "#initialize with no args" do
+    expected_uuid = UUID.new
+
+    # expected_uuid.variant.should eq UUID::Variant::RFC4122
+    # expected_uuid.version.should eq 4_u8
+  end
+
+  it "#initialize from strings" do
+    expected_uuid = UUID.new("c20335c3-7f46-4126-aae9-f665434ad12b")
+
+    expected_uuid.should eq UUID.new("c20335c3-7f46-4126-aae9-f665434ad12b")
+    expected_uuid.should eq UUID.new("C20335C3-7F46-4126-AAE9-F665434AD12B")
+    expected_uuid.should eq UUID.new("c20335c37f464126aae9f665434ad12b")
+    expected_uuid.should eq UUID.new("C20335C37F464126AAE9F665434AD12B")
+    expected_uuid.should eq UUID.new("urn:uuid:c20335c3-7f46-4126-aae9-f665434ad12b")
+  end
+
+  # it "#initialize from array" do
+  #   expected_uuid = UUID.new([0_u8, 1_u8, 2_u8, 3_u8, 4_u8, 5_u8, 6_u8, 7_u8,
+  #                             8_u8, 9_u8, 10_u8, 11_u8, 12_u8, 13_u8, 14_u8, 15_u8])
+
+  #   # expected_uuid.variant.should eq UUID::Variant::RFC4122
+  #   # expected_uuid.version.should eq 4_u8
+  #   expected_uuid.to_s.should    eq "00010203-0405-0607-0809-0a0b0c0d0e0f"
+  # end
+
+  # it "#initialize has the correct version and variant" do
+  #   expected_uuid = UUID.new
+
+  #   expected_uuid.variant.should eq UUID::Variant::RFC4122
+  #   expected_uuid.version.should eq 4_u8
+  # end
+
+  # it "#initialize with args has the correct version and variant" do
+  #   expected_string_uuid = UUID.new("c20335c3-7f46-4126-aae9-f665434ad12b")
+
+  #   expected_string_uuid.variant.should eq UUID::Variant::RFC4122
+  #   expected_string_uuid.version.should eq 4_u8
+  # end
+
+  # it "#== with String" do end
+  # it "#== with Array" do end
+  # it "#to_a" do end
+  # it "#to_s" do end
+  # it "#to_s with format" do end
+
+  # it "#version" do end
+  # it "#version=" do end
+  # it "#variant" do end
+  # it "#variant=" do end
+
+  # it "class level decodes to UUID" do
+  #   expected_uuid = UUID.new("c20335c3-7f46-4126-aae9-f665434ad12b")
+
+  #   expected_uuid.should eq UUID.decode("c20335c3-7f46-4126-aae9-f665434ad12b")
+  #   expected_uuid.should eq UUID.decode("c20335c37f464126aae9f665434ad12b")
+  #   expected_uuid.should eq UUID.decode("urn:uuid:c20335c3-7f46-4126-aae9-f665434ad12b")
+  # end
+
+  # it "#decodes to UUID" do
+  #   expected_uuid = UUID.new("c20335c3-7f46-4126-aae9-f665434ad12b")
+
+  #   actual_hypenated_uuid = UUID.new
+  #   actual_hexstring_uuid = UUID.new
+  #   actual_urn_uuid = UUID.new
+
+  #   expected_uuid.should eq actual_hypenated_uuid.decode("c20335c3-7f46-4126-aae9-f665434ad12b")
+  #   expected_uuid.should eq actual_hexstring_uuid.decode("c20335c37f464126aae9f665434ad12b")
+  #   expected_uuid.should eq actual_urn_uuid.decode("urn:uuid:c20335c3-7f46-4126-aae9-f665434ad12b")
+  # end
+
+  # it "#encodes to string in different formats" do
+  #   expected_uuid = UUID.new("c20335c3-7f46-4126-aae9-f665434ad12b")
+
+  #   expected_uuid.encode.should              eq "c20335c3-7f46-4126-aae9-f665434ad12b"
+  #   expected_uuid.encode(:hyphenated).should eq "c20335c3-7f46-4126-aae9-f665434ad12b"
+  #   expected_uuid.encode(:hexstring).should  eq "c20335c37f464126aae9f665434ad12b"
+  #   expected_uuid.encode(:urn).should        eq "urn:uuid:c20335c3-7f46-4126-aae9-f665434ad12b"
+  # end
+end
diff --git a/src/uuid.cr b/src/uuid.cr
new file mode 100644
index 000000000000..17039ab11f8e
--- /dev/null
+++ b/src/uuid.cr
@@ -0,0 +1,268 @@
+require "secure_random"
+
+# Universally Unique IDentifier.
+#
+# Supports custom variants with arbitrary 16 bytes as well as (RFC 4122)[https://www.ietf.org/rfc/rfc4122.txt] variant
+# versions.
+struct UUID
+  enum Variant # UUID variants.
+    Unknown    # Unknown (ie. custom, your own).
+    NCS        # Reserved by the NCS for backward compatibility.
+    RFC4122    # As described in the RFC4122 Specification (default).
+    Microsoft  # Reserved by Microsoft for backward compatibility.
+    Future     # Reserved for future expansion.
+  end
+
+  # Generates a new `UUID` in the RFC 4122 v4 UUID format.
+  # ```
+  # uuid = UUID.new
+  # uuid.to_s # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # ```
+  ## TODO: should we set version?
+  def initialize
+    @bytes = SecureRandom.random_bytes(16).to_a
+    self.variant = Variant::RFC4122
+    self.version = 4_u8
+  end
+
+  # Generates a new `UUID` from a 16-`bytes` Array..
+  # ```
+  # arr = [0_u8, 1_u8, 2_u8, 3_u8, 4_u8, 5_u8, 6_u8, 7_u8, 8_u8, 9_u8, 10_u8, 11_u8, 12_u8, 13_u8, 14_u8, 15_u8]
+  # uuid = UUID.new(arr)
+  # uuid.to_s # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # ```
+  ## TODO: use instance_sizeof() to see if it can be coersed into UUID
+  ## TODO: should we set version?
+  def initialize(new_bytes : Array(UInt8))
+    raise ArgumentError.new "Invalid bytes length #{new_bytes.size}, expected 16." if new_bytes.size != 16
+    @bytes = new_bytes
+    # self.variant = Variant::RFC4122
+    # self.version = 4_u8
+  end
+
+  # Generates a new `UUID` from string `value`.
+  # See `UUID#decode(value : String)` for details on supported string formats.
+  # ```
+  # value = "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # uuid = UUID.new(value)
+  # uuid.to_s # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # ```
+  def initialize(new_bytes : String)
+    @bytes = Array(UInt8).new
+    decode new_bytes
+  end
+
+  # Returns `true` if `other` string represents the same UUID, `false` otherwise.
+  # ```
+  # value1 = "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # value2 = "ee843b26-56d8-472b-b343-0b94ed9077ff"
+  # uuid1  = UUID.new(value1)
+  # uuid2  = UUID.new(value2)
+  # uuid1 == uuid1.to_s # => true
+  # uuid1 == uuid2.to_s # => false
+  # ```
+  def ==(other : String)
+    self == UUID.new other
+  end
+
+  # Returns `true` if `other` static 16 bytes represent the same UUID, `false` otherwise.
+  # ```
+  # arr1  = [0_u8, 1_u8, 2_u8, 3_u8, 4_u8, 5_u8, 6_u8, 7_u8, 8_u8, 9_u8, 10_u8, 11_u8, 12_u8, 13_u8, 14_u8, 15_u8]
+  # arr2  = [15_u8, 14_u8, 13_u8, 12_u8, 11_u8, 10_u8, 9_u8, 8_u8, 7_u8, 6_u8, 5_u8, 4_u8, 3_u8, 2_u8, 1_u8, 0_u8]
+  # uuid1 = UUID.new(arr1)
+  # uuid2 = UUID.new(arr2)
+  # uuid1 == uuid1.to_a # => true
+  # uuid1 == uuid2.to_a # => false
+  # ```
+  def ==(other : Array(UInt8))
+    self.to_a == other
+  end
+
+  # Returns the internal Representation of the UUID as an `Array(UInt8)`.
+  # ```
+  # arr  = [0_u8, 1_u8, 2_u8, 3_u8, 4_u8, 5_u8, 6_u8, 7_u8, 8_u8, 9_u8, 10_u8, 11_u8, 12_u8, 13_u8, 14_u8, 15_u8]
+  # uuid = UUID.new(arr)
+  # uuid.to_a # => [0_u8, 1_u8, 2_u8, 3_u8, 4_u8, 5_u8, 6_u8, 7_u8, 8_u8, 9_u8, 10_u8, 11_u8, 12_u8, 13_u8, 14_u8, 15_u8]
+  # ```
+  def to_a
+    @bytes
+  end
+
+  # Writes a hyphenated format String to `io`.
+  # See `UUID#encode(format : Symbol)` for details on String encoding.
+  # ```
+  # uuid = UUID.new
+  # uuid.to_s # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # ```
+  def to_s(io : IO)
+    io << encode
+  end
+
+  # Writes a String to `io` with *args*.
+  # See `UUID#encode(format : Symbol)` for details on String encoding.
+  # ```
+  # uuid = UUID.new
+  # uuid.to_s(:hexstring) # => "c20335c37f464126aae9f665434ad12b"
+  # ```
+  def to_s(io : IO, format : Symbol)
+    io << encode(format)
+  end
+
+  # Returns version based on RFC 4122 format. See also `UUID#variant`.
+  # ```
+  # uuid = UUID.new
+  # uuid.version # => 4
+  # ```
+  def version
+    @bytes[6] >> 4
+  end
+
+  # Sets version to a specified `value`.
+  # Doesn't set variant (see `UUID#variant=(value : UInt8)`).
+  # ```
+  # uuid = UUID.new
+  # uuid.version = 4_u8
+  # uuid.version # => 4
+  # ```
+  def version=(version : UInt8)
+    @bytes[6] = (@bytes[6] & 0xf) | (version << 4)
+  end
+
+  # Returns `UUID` variant.
+  # Values for this are documented at `UUID#Variant`
+  # ```
+  # uuid = UUID.new
+  # uuid.variant # => UUID::Variant::RFC4122
+  # ```
+  def variant
+    case
+    when @bytes[8] & 0x80 == 0x00
+      Variant::NCS
+    when @bytes[8] & 0xc0 == 0x80
+      Variant::RFC4122
+    when @bytes[8] & 0xe0 == 0xc0
+      Variant::Microsoft
+    when @bytes[8] & 0xe0 == 0xe0
+      Variant::Future
+    else
+      Variant::Unknown
+    end
+  end
+
+  # Sets `UUID` variant to specified `variant`.
+  # Values for this are documented at `UUID#Variant`
+  # ```
+  # uuid = UUID.new
+  # uuid.variant = UUID::Variant::RFC4122
+  # uuid.variant # => UUID::Variant::RFC4122
+  # ```
+  def variant=(variant : Variant)
+    case variant
+    when Variant::NCS
+      @bytes[8] = @bytes[8] & 0x7f
+    when Variant::RFC4122
+      @bytes[8] = (@bytes[8] & 0x3f) | 0x80
+    when Variant::Microsoft
+      @bytes[8] = (@bytes[8] & 0x1f) | 0xc0
+    when Variant::Future
+      @bytes[8] = (@bytes[8] & 0x1f) | 0xe0
+    else
+      raise ArgumentError.new "Can't set unknown variant."
+    end
+  end
+
+
+  # Generates a `UUID` from a formatted `UUID` String.
+  # See `UUID#encode(format : Symbol)` for details on String encoding.
+  # ```
+  # uuid1 = UUID.decode("c20335c3-7f46-4126-aae9-f665434ad12b")
+  # uuid2 = UUID.decode("c20335c37f464126aae9f665434ad12b")
+  # uuid3 = UUID.decode("urn:uuid:c20335c3-7f46-4126-aae9-f665434ad12b")
+  # uuid1.to_s # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # uuid2.to_s # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # uuid3.to_s # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # ```
+  def self.decode(value : String)
+    value = value.delete("urn:uuid:") if value.starts_with? "urn:uuid:"
+    value = value.delete('-') if [value[8], value[13], value[18], value[23]] == Array.new(4, '-')
+    raise ArgumentError.new "Invalid UUID provided" if value.size != 32
+
+    results = Array(UInt8).new
+    char_iterator = value.each_char
+    16.times do |index|
+      char_pair = [char_iterator.next.to_s, char_iterator.next.to_s]
+      # raise ArgumentError.new "Invalid UUID char format" unless char_pair.all?(&.hex?)
+      results << char_pair.join.to_u8(16)
+    end
+
+    new(results)
+  end
+
+  # Generates a `UUID` from a formatted `UUID` String.
+  # See `UUID#encode(format : Symbol)` for details on String encoding.
+  # Hyphenated Format
+  # ```
+  # uuid = UUID.new
+  # uuid.to_s # => "ee843b26-56d8-472b-b343-0b94ed9077ff"
+  # uuid.decode("c20335c3-7f46-4126-aae9-f665434ad12b")
+  # uuid.to_s # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # ```
+  # Hexstring Format
+  # ```
+  # uuid = UUID.new
+  # uuid.to_s # => "ee843b26-56d8-472b-b343-0b94ed9077ff"
+  # uuid.decode("c20335c37f464126aae9f665434ad12b")
+  # uuid.to_s # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # ```
+  # URN Format
+  # ```
+  # uuid = UUID.new
+  # uuid.to_s # => "ee843b26-56d8-472b-b343-0b94ed9077ff"
+  # uuid.decode("urn:uuid:c20335c3-7f46-4126-aae9-f665434ad12b")
+  # uuid.to_s # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # ```
+  def decode(value : String)
+    value = value[0..8] if value.starts_with? "urn:uuid:"
+    value = value.delete('-') if [value[8], value[13], value[18], value[23]] == Array.new(4, '-')
+    raise ArgumentError.new "Invalid UUID provided" if value.size != 32
+
+    # value.each_char.each_combination(2) do |pair|
+      # raise ArgumentError.new "Invalid UUID char format" unless char_pair.all?(&.hex?)
+      value.each_char do |char|
+        @bytes << char.to_i(16).to_u8
+      end
+    # end
+
+    @bytes
+  end
+
+  # Generates a String representing a `UUID`
+  # Hyphenated Format contains '-' between after the 2nd, 3rd, 4th, 5th byte
+  # ```
+  # uuid = UUID.new
+  # uuid.encode              # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # uuid.encode(:hyphenated) # => "c20335c3-7f46-4126-aae9-f665434ad12b"
+  # ```
+  # Hexstring Format is a 32 character String of "0-9" or "a-z" or "A-Z"
+  # ```
+  # uuid = UUID.new
+  # uuid.encode(:hexstring)  # => "c20335c37f464126aae9f665434ad12b"
+  # ```
+  # URN Format begins with `"urn:uuid:"` and then a Hyphonated Fromat String
+  # ```
+  # uuid = UUID.new
+  # uuid.encode(:urn)        # => "urn:uuid:c20335c3-7f46-4126-aae9-f665434ad12b"
+  # ```
+  def encode(format = :hyphenated)
+    case format
+    when :hyphenated
+      "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x" % @bytes
+    when :hexstring
+      "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x" % @bytes
+    when :urn
+      "urn:uuid:%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x" % @bytes
+    else
+      raise ArgumentError.new "Unexpected format #{format}."
+    end
+  end
+end