diff --git a/go.mod b/go.mod
index 81af465..3dc147b 100644
--- a/go.mod
+++ b/go.mod
@@ -5,6 +5,7 @@
 	github.com/cockroachdb/apd/v2 v2.0.1
 	github.com/emicklei/proto v1.6.15
 	github.com/google/go-cmp v0.4.0
+	github.com/google/uuid v1.2.0
 	github.com/kr/pretty v0.1.0
 	github.com/kylelemons/godebug v1.1.0
 	github.com/lib/pq v1.0.0 // indirect
diff --git a/go.sum b/go.sum
index 8c5d68a..cfe3f2b 100644
--- a/go.sum
+++ b/go.sum
@@ -45,8 +45,8 @@
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
 github.com/google/go-cmp v0.4.0 h1:xsAVV57WRhGj6kEIi8ReJzQlHHqcBYCElAvkovg3B/4=
 github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
-github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
-github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/uuid v1.2.0 h1:qJYtXnJRWmpe7m/3XlyhrsLrEURqHRM2kxzoxXqyUDs=
+github.com/google/uuid v1.2.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/gorilla/websocket v1.4.0/go.mod h1:E7qHFY5m1UJ88s3WnNqhKjPHQ0heANvMoAMk2YaljkQ=
 github.com/grpc-ecosystem/go-grpc-middleware v1.0.0/go.mod h1:FiyG127CGDf3tlThmgyCl78X/SZQqEOJBCDaAfeWzPs=
 github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0/go.mod h1:8NvIoxWQoOIhqOTXgfV/d3M/q6VIi02HzZEHgUlZvzk=
diff --git a/pkg/register.go b/pkg/register.go
index 69bdb0c..fdfc1c3 100644
--- a/pkg/register.go
+++ b/pkg/register.go
@@ -45,4 +45,5 @@
 	_ "cuelang.org/go/pkg/tool/file"
 	_ "cuelang.org/go/pkg/tool/http"
 	_ "cuelang.org/go/pkg/tool/os"
+	_ "cuelang.org/go/pkg/uuid"
 )
diff --git a/pkg/uuid/pkg.go b/pkg/uuid/pkg.go
new file mode 100644
index 0000000..ae2be7e
--- /dev/null
+++ b/pkg/uuid/pkg.go
@@ -0,0 +1,159 @@
+// Code generated by go generate. DO NOT EDIT.
+
+//go:generate rm pkg.go
+//go:generate go run ../gen/gen.go
+
+package uuid
+
+import (
+	"cuelang.org/go/internal/core/adt"
+	"cuelang.org/go/pkg/internal"
+)
+
+func init() {
+	internal.Register("uuid", pkg)
+}
+
+var _ = adt.TopKind // in case the adt package isn't used
+
+var pkg = &internal.Package{
+	Native: []*internal.Builtin{{
+		Name: "Valid",
+		Params: []internal.Param{
+			{Kind: adt.StringKind},
+		},
+		Result: adt.BottomKind,
+		Func: func(c *internal.CallCtxt) {
+			s := c.String(0)
+			if c.Do() {
+				c.Ret = Valid(s)
+			}
+		},
+	}, {
+		Name: "Parse",
+		Params: []internal.Param{
+			{Kind: adt.StringKind},
+		},
+		Result: adt.StringKind,
+		Func: func(c *internal.CallCtxt) {
+			s := c.String(0)
+			if c.Do() {
+				c.Ret, c.Err = Parse(s)
+			}
+		},
+	}, {
+		Name: "ToString",
+		Params: []internal.Param{
+			{Kind: adt.StringKind},
+		},
+		Result: adt.StringKind,
+		Func: func(c *internal.CallCtxt) {
+			x := c.String(0)
+			if c.Do() {
+				c.Ret = ToString(x)
+			}
+		},
+	}, {
+		Name: "URN",
+		Params: []internal.Param{
+			{Kind: adt.StringKind},
+		},
+		Result: adt.StringKind,
+		Func: func(c *internal.CallCtxt) {
+			x := c.String(0)
+			if c.Do() {
+				c.Ret, c.Err = URN(x)
+			}
+		},
+	}, {
+		Name: "FromInt",
+		Params: []internal.Param{
+			{Kind: adt.IntKind},
+		},
+		Result: adt.StringKind,
+		Func: func(c *internal.CallCtxt) {
+			i := c.BigInt(0)
+			if c.Do() {
+				c.Ret, c.Err = FromInt(i)
+			}
+		},
+	}, {
+		Name: "ToInt",
+		Params: []internal.Param{
+			{Kind: adt.StringKind},
+		},
+		Result: adt.IntKind,
+		Func: func(c *internal.CallCtxt) {
+			x := c.String(0)
+			if c.Do() {
+				c.Ret = ToInt(x)
+			}
+		},
+	}, {
+		Name: "Variant",
+		Params: []internal.Param{
+			{Kind: adt.StringKind},
+		},
+		Result: adt.IntKind,
+		Func: func(c *internal.CallCtxt) {
+			x := c.String(0)
+			if c.Do() {
+				c.Ret, c.Err = Variant(x)
+			}
+		},
+	}, {
+		Name: "Version",
+		Params: []internal.Param{
+			{Kind: adt.StringKind},
+		},
+		Result: adt.IntKind,
+		Func: func(c *internal.CallCtxt) {
+			x := c.String(0)
+			if c.Do() {
+				c.Ret, c.Err = Version(x)
+			}
+		},
+	}, {
+		Name: "SHA1",
+		Params: []internal.Param{
+			{Kind: adt.StringKind},
+			{Kind: adt.BytesKind | adt.StringKind},
+		},
+		Result: adt.StringKind,
+		Func: func(c *internal.CallCtxt) {
+			space, data := c.String(0), c.Bytes(1)
+			if c.Do() {
+				c.Ret, c.Err = SHA1(space, data)
+			}
+		},
+	}, {
+		Name: "MD5",
+		Params: []internal.Param{
+			{Kind: adt.StringKind},
+			{Kind: adt.BytesKind | adt.StringKind},
+		},
+		Result: adt.StringKind,
+		Func: func(c *internal.CallCtxt) {
+			space, data := c.String(0), c.Bytes(1)
+			if c.Do() {
+				c.Ret, c.Err = MD5(space, data)
+			}
+		},
+	}},
+	CUE: `{
+	ns: {
+		DNS:  "6ba7b810-9dad-11d1-80b4-00c04fd430c8"
+		URL:  "6ba7b811-9dad-11d1-80b4-00c04fd430c8"
+		OID:  "6ba7b812-9dad-11d1-80b4-00c04fd430c8"
+		X500: "6ba7b814-9dad-11d1-80b4-00c04fd430c8"
+		Nil:  "00000000-0000-0000-0000-000000000000"
+	}
+	variants: {
+		Invalid:   0
+		RFC4122:   1
+		Reserved:  2
+		Microsoft: 3
+		Future:    4
+	}
+}`,
+}
diff --git a/pkg/uuid/testdata/uuid.txtar b/pkg/uuid/testdata/uuid.txtar
new file mode 100644
index 0000000..bcae1eb
--- /dev/null
+++ b/pkg/uuid/testdata/uuid.txtar
@@ -0,0 +1,69 @@
+-- in.cue --
+import "uuid"
+
+sha1: a: uuid.SHA1(uuid.ns.DNS, "cuelang.org")
+
+md5: a: uuid.MD5(uuid.ns.URL, "https://cuelang.org")
+
+valid: {
+    a: uuid.Valid
+    a: "052ef62d-7223-58b6-a551-c1deee46d401"
+}
+
+invalid: {
+    a: uuid.Valid
+    a: "052EF62D-7223-58B6-A551-C1DEEE46D401"
+
+    b: uuid.Valid
+    b: "052ef62d_7223_58b6_a551_c1deee46d401"
+}
+
+parse: a: uuid.Parse("052ef62d722358b6a551c1deee46d401")
+
+fromInt: a: uuid.FromInt(0x052ef62d_7223_58b6_a551_c1deee46d401)
+
+variant: a: uuid.Variant(sha1.a)
+version: a: uuid.Version(sha1.a)
+urn: a: uuid.URN(sha1.a)
+toInt: a: uuid.ToInt(sha1.a)
+
+-- out/uuid --
+Errors:
+invalid.a: invalid value "052EF62D-7223-58B6-A551-C1DEEE46D401" (does not satisfy uuid.Valid): invalid UUID "052EF62D-7223-58B6-A551-C1DEEE46D401":
+    ./in.cue:14:8
+invalid.b: invalid value "052ef62d_7223_58b6_a551_c1deee46d401" (does not satisfy uuid.Valid): invalid UUID "052ef62d_7223_58b6_a551_c1deee46d401":
+    ./in.cue:17:8
+
+Result:
+sha1: {
+	a: "052ef62d-7223-58b6-a551-c1deee46d401"
+}
+md5: {
+	a: "d891d69e-ae5c-39e0-9ead-164abd207f1f"
+}
+valid: {
+	a: "052ef62d-7223-58b6-a551-c1deee46d401"
+}
+invalid: {
+	a: _|_ // invalid.a: invalid value "052EF62D-7223-58B6-A551-C1DEEE46D401" (does not satisfy uuid.Valid): invalid.a: invalid UUID "052EF62D-7223-58B6-A551-C1DEEE46D401"
+	b: _|_ // invalid.b: invalid value "052ef62d_7223_58b6_a551_c1deee46d401" (does not satisfy uuid.Valid): invalid.b: invalid UUID "052ef62d_7223_58b6_a551_c1deee46d401"
+}
+parse: {
+	a: "052ef62d-7223-58b6-a551-c1deee46d401"
+}
+fromInt: {
+	a: "052ef62d-7223-58b6-a551-c1deee46d401"
+}
+variant: {
+	a: 1
+}
+version: {
+	a: 5
+}
+urn: {
+	a: "urn:uuid:052ef62d-7223-58b6-a551-c1deee46d401"
+}
+toInt: {
+	a: 93651793875903522077150095950593860979557386807737776869062002310283964632724204171313
+}
+
diff --git a/pkg/uuid/uuid.cue b/pkg/uuid/uuid.cue
new file mode 100644
index 0000000..4efd256
--- /dev/null
+++ b/pkg/uuid/uuid.cue
@@ -0,0 +1,35 @@
+// Copyright 2021 CUE Authors
+// 
+// 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.
+
+package uuid
+
+// Predefined namespaces
+ns: {
+	DNS:  "6ba7b810-9dad-11d1-80b4-00c04fd430c8"
+	URL:  "6ba7b811-9dad-11d1-80b4-00c04fd430c8"
+	OID:  "6ba7b812-9dad-11d1-80b4-00c04fd430c8"
+	X500: "6ba7b814-9dad-11d1-80b4-00c04fd430c8"
+	Nil:  "00000000-0000-0000-0000-000000000000"
+}
+
+// Invalid UUID
+variants: Invalid: 0
+// The variant specified in RFC4122
+variants: RFC4122: 1
+// Reserved, NCS backward compatibility.
+variants: Reserved: 2
+// Reserved, Microsoft Corporation backward compatibility.
+variants: Microsoft: 3
+// Reserved for future definition.
+variants: Future: 4
diff --git a/pkg/uuid/uuid.go b/pkg/uuid/uuid.go
new file mode 100644
index 0000000..9d55517
--- /dev/null
+++ b/pkg/uuid/uuid.go
@@ -0,0 +1,121 @@
+// Copyright 2021 CUE Authors
+//
+// 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.
+
+// Package uuid defines functionality for creating UUIDs as defined in RFC 4122.
+//
+// Currently only Version 5 (SHA1) and Version 3 (MD5) are supported.
+package uuid
+
+import (
+	"fmt"
+	"math/big"
+	"regexp"
+
+	"github.com/google/uuid"
+)
+
+var valid = regexp.MustCompile(
+	"^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$")
+
+// Valid can be used to define a valid Valid.
+func Valid(s string) error {
+	if !valid.MatchString(string(s)) {
+		return fmt.Errorf("invalid UUID %q", s)
+	}
+	return nil
+}
+
+// Parse decodes s into a UUID or returns an error. Both the standard UUID forms
+// of xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx and
+// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx are decoded as well as the
+// Microsoft encoding {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} and the raw hex
+// encoding: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.
+func Parse(s string) (string, error) {
+	x, err := uuid.Parse(s)
+	return string(x.String()), err
+}
+
+// String represents a 128-bit UUID value as a string.
+func ToString(x string) string {
+	return string(x)
+}
+
+// URN reports the canonical URN of a UUID.
+func URN(x string) (string, error) {
+	u, err := uuid.Parse(string(x))
+	if err != nil {
+		return "", err
+	}
+	return u.URN(), nil
+}
+
+// FromInt creates a UUID from an integer.
+//
+//    DNS:  uuid.FromInt(0x6ba7b810_9dad_11d1_80b4_00c04fd430c8)
+//
+func FromInt(i *big.Int) (string, error) {
+	// must be uint128
+	var buf [16]byte
+	b := i.Bytes()
+	if len(b) < 16 {
+		copy(buf[16-len(b):], b)
+		b = buf[:]
+	}
+	u, err := uuid.FromBytes(b)
+	return string(u.String()), err
+}
+
+// ToInt represents a UUID string as a 128-bit value.
+func ToInt(x string) *big.Int {
+	var i big.Int
+	i.SetBytes([]byte(x[:]))
+	return &i
+}
+
+// Variant reports the UUID variant.
+func Variant(x string) (int, error) {
+	u, err := uuid.Parse(string(x))
+	if err != nil {
+		return 0, err
+	}
+	return int(u.Variant()), nil
+}
+
+// Version reports the UUID version.
+func Version(x string) (int, error) {
+	u, err := uuid.Parse(string(x))
+	if err != nil {
+		return 0, err
+	}
+	return int(u.Version()), nil
+}
+
+// SHA1 generates a version 5 UUID based on the supplied name space and data.
+func SHA1(space string, data []byte) (string, error) {
+	u, err := uuid.Parse(string(space))
+	if err != nil {
+		return "", err
+	}
+	return string(uuid.NewSHA1(u, data).String()), nil
+}
+
+// MD5 generates a version 3 UUID based on the supplied name space and data.
+// Use SHA1 instead if you can.
+func MD5(space string, data []byte) (string, error) {
+	u, err := uuid.Parse(string(space))
+	if err != nil {
+		return "", err
+	}
+	return string(uuid.NewMD5(u, data).String()), nil
+}
diff --git a/pkg/uuid/uuid_test.go b/pkg/uuid/uuid_test.go
new file mode 100644
index 0000000..70c2dc1
--- /dev/null
+++ b/pkg/uuid/uuid_test.go
@@ -0,0 +1,25 @@
+// Copyright 2020 CUE Authors
+//
+// 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.
+
+package uuid_test
+
+import (
+	"testing"
+
+	"cuelang.org/go/pkg/internal/builtintest"
+)
+
+func TestBuiltin(t *testing.T) {
+	builtintest.Run("uuid", t)
+}