diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000000..bd97bd412a
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,22 @@
+on: [push, pull_request]
+name: Test
+jobs:
+  test:
+    strategy:
+      matrix:
+        go-version: [1.11.x, 1.12.x, 1.13.x, 1.14.x, 1.15.x, 1.16.x]
+        os: [ubuntu-latest, macos-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Install Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: ${{ matrix.go-version }}
+    - name: Checkout code
+      uses: actions/checkout@v2
+    - name: TestLatest
+      if: matrix.go-version == '1.16.x'
+      run: ./test.bash
+    - name: TestAll
+      if: matrix.go-version != '1.16.x'
+      run: go test ./...
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 0b5166678a..0000000000
--- a/.travis.yml
+++ /dev/null
@@ -1,22 +0,0 @@
-language: go
-before_install:
-  - mkdir /tmp/go1.12
-  - curl -L -s https://dl.google.com/go/go1.12.linux-amd64.tar.gz | tar -zxf - -C /tmp/go1.12 --strip-components 1
-  - unset GOROOT
-  - (GO111MODULE=on /tmp/go1.12/bin/go mod vendor)
-matrix:
-  include:
-    - go: 1.9.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.10.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.11.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.12.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.13.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.14.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.15.x
-      script: ./test.bash
diff --git a/descriptor/descriptor.go b/descriptor/descriptor.go
index c3c4a2b87e..ffde8a6508 100644
--- a/descriptor/descriptor.go
+++ b/descriptor/descriptor.go
@@ -79,14 +79,9 @@ func deriveRawDescriptor(d protoreflect.Descriptor) ([]byte, []int) {
 	}
 
 	// Obtain the raw file descriptor.
-	var raw []byte
-	switch fd := d.(type) {
-	case interface{ ProtoLegacyRawDesc() []byte }:
-		raw = fd.ProtoLegacyRawDesc()
-	case protoreflect.FileDescriptor:
-		raw, _ = proto.Marshal(protodesc.ToFileDescriptorProto(fd))
-	}
-	file := protoimpl.X.CompressGZIP(raw)
+	fd := d.(protoreflect.FileDescriptor)
+	b, _ := proto.Marshal(protodesc.ToFileDescriptorProto(fd))
+	file := protoimpl.X.CompressGZIP(b)
 
 	// Reverse the indexes, since we populated it in reverse.
 	for i, j := 0, len(idxs)-1; i < j; i, j = i+1, j-1 {
diff --git a/go.mod b/go.mod
index 67adeed862..6cac17b113 100644
--- a/go.mod
+++ b/go.mod
@@ -1,8 +1,9 @@
+// Deprecated: Use the "google.golang.org/protobuf" module instead.
 module github.com/golang/protobuf
 
 go 1.9
 
 require (
-	github.com/google/go-cmp v0.4.0
-	google.golang.org/protobuf v1.23.0
+	github.com/google/go-cmp v0.5.5
+	google.golang.org/protobuf v1.26.0
 )
diff --git a/go.sum b/go.sum
index 92baf2631b..20a6257f1b 100644
--- a/go.sum
+++ b/go.sum
@@ -1,18 +1,8 @@
-github.com/golang/protobuf v1.4.0-rc.1/go.mod h1:ceaxUfeHdC40wWswd/P6IGgMaK3YpKi5j83Wpe3EHw8=
-github.com/golang/protobuf v1.4.0-rc.1.0.20200221234624-67d41d38c208/go.mod h1:xKAWHe0F5eneWXFV3EuXVDTCmh+JuBKY0li0aMyXATA=
-github.com/golang/protobuf v1.4.0-rc.2/go.mod h1:LlEzMj4AhA7rCAGe4KMBDvJI+AwstrUpVNzEA03Pprs=
-github.com/golang/protobuf v1.4.0-rc.4.0.20200313231945-b860323f09d0/go.mod h1:WU3c8KckQ9AFe+yFwt9sWVRKCVIyN9cPHBJSNnbL67w=
-github.com/golang/protobuf v1.4.0/go.mod h1:jodUvKwWbYaEsadDk5Fwe5c77LiNKVO9IDvqG2KuDX0=
-github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
-github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
-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/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
+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=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-google.golang.org/protobuf v0.0.0-20200109180630-ec00e32a8dfd/go.mod h1:DFci5gLYBciE7Vtevhsrf46CRTquxDuWsQurQQe4oz8=
-google.golang.org/protobuf v0.0.0-20200221191635-4d8936d0db64/go.mod h1:kwYJMbMJ01Woi6D6+Kah6886xMZcty6N08ah7+eCXa0=
-google.golang.org/protobuf v0.0.0-20200228230310-ab0ca4ff8a60/go.mod h1:cfTl7dwQJ+fmap5saPgwCLgHXTUD7jkjRqWcaiX5VyM=
-google.golang.org/protobuf v1.20.1-0.20200309200217-e05f789c0967/go.mod h1:A+miEFZTKqfCUM6K7xSMQL9OKL/b6hQv+e19PK+JZNE=
-google.golang.org/protobuf v1.21.0/go.mod h1:47Nbq4nVaFHyn7ilMalzfO3qCViNmqZ2kzikPIcrTAo=
-google.golang.org/protobuf v1.23.0 h1:4MY060fB1DLGMB/7MBTLnwQUY6+F09GEiz6SsrNqyzM=
-google.golang.org/protobuf v1.23.0/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2l/sGQquU=
+google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
+google.golang.org/protobuf v1.26.0 h1:bxAC2xTBsZGibn2RTntX0oH50xLsqy1OxA9tTL3p/lk=
+google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
diff --git a/jsonpb/decode.go b/jsonpb/decode.go
index 7c6c5a5244..60e82caa9a 100644
--- a/jsonpb/decode.go
+++ b/jsonpb/decode.go
@@ -135,14 +135,14 @@ func (u *Unmarshaler) unmarshalMessage(m protoreflect.Message, in []byte) error
 	md := m.Descriptor()
 	fds := md.Fields()
 
-	if string(in) == "null" && md.FullName() != "google.protobuf.Value" {
-		return nil
-	}
-
 	if jsu, ok := proto.MessageV1(m.Interface()).(JSONPBUnmarshaler); ok {
 		return jsu.UnmarshalJSONPB(u, in)
 	}
 
+	if string(in) == "null" && md.FullName() != "google.protobuf.Value" {
+		return nil
+	}
+
 	switch wellKnownType(md.FullName()) {
 	case "Any":
 		var jsonObject map[string]json.RawMessage
@@ -332,11 +332,12 @@ func (u *Unmarshaler) unmarshalMessage(m protoreflect.Message, in []byte) error
 			raw = v
 		}
 
+		field := m.NewField(fd)
 		// Unmarshal the field value.
-		if raw == nil || (string(raw) == "null" && !isSingularWellKnownValue(fd)) {
+		if raw == nil || (string(raw) == "null" && !isSingularWellKnownValue(fd) && !isSingularJSONPBUnmarshaler(field, fd)) {
 			continue
 		}
-		v, err := u.unmarshalValue(m.NewField(fd), raw, fd)
+		v, err := u.unmarshalValue(field, raw, fd)
 		if err != nil {
 			return err
 		}
@@ -364,11 +365,12 @@ func (u *Unmarshaler) unmarshalMessage(m protoreflect.Message, in []byte) error
 			return fmt.Errorf("extension field %q does not extend message %q", xname, m.Descriptor().FullName())
 		}
 
+		field := m.NewField(fd)
 		// Unmarshal the field value.
-		if raw == nil || (string(raw) == "null" && !isSingularWellKnownValue(fd)) {
+		if raw == nil || (string(raw) == "null" && !isSingularWellKnownValue(fd) && !isSingularJSONPBUnmarshaler(field, fd)) {
 			continue
 		}
-		v, err := u.unmarshalValue(m.NewField(fd), raw, fd)
+		v, err := u.unmarshalValue(field, raw, fd)
 		if err != nil {
 			return err
 		}
@@ -390,6 +392,14 @@ func isSingularWellKnownValue(fd protoreflect.FieldDescriptor) bool {
 	return false
 }
 
+func isSingularJSONPBUnmarshaler(v protoreflect.Value, fd protoreflect.FieldDescriptor) bool {
+	if fd.Message() != nil && fd.Cardinality() != protoreflect.Repeated {
+		_, ok := proto.MessageV1(v.Interface()).(JSONPBUnmarshaler)
+		return ok
+	}
+	return false
+}
+
 func (u *Unmarshaler) unmarshalValue(v protoreflect.Value, in []byte, fd protoreflect.FieldDescriptor) (protoreflect.Value, error) {
 	switch {
 	case fd.IsList():
diff --git a/jsonpb/json_test.go b/jsonpb/json_test.go
index 0ef23f2d30..a98ad169f2 100644
--- a/jsonpb/json_test.go
+++ b/jsonpb/json_test.go
@@ -1009,7 +1009,7 @@ func TestUnmarshalNullWithJSONPBUnmarshaler(t *testing.T) {
 		t.Errorf("unmarshal error: %v", err)
 	}
 
-	want := ptrFieldMessage{}
+	want := ptrFieldMessage{StringField: &stringField{IsSet: true, StringValue: "null"}}
 	if !proto.Equal(&ptrFieldMsg, &want) {
 		t.Errorf("unmarshal result StringField: got %v, want %v", ptrFieldMsg, want)
 	}
diff --git a/proto/registry.go b/proto/registry.go
index 1e7ff64205..066b4323b4 100644
--- a/proto/registry.go
+++ b/proto/registry.go
@@ -13,6 +13,7 @@ import (
 	"strings"
 	"sync"
 
+	"google.golang.org/protobuf/reflect/protodesc"
 	"google.golang.org/protobuf/reflect/protoreflect"
 	"google.golang.org/protobuf/reflect/protoregistry"
 	"google.golang.org/protobuf/runtime/protoimpl"
@@ -62,14 +63,7 @@ func FileDescriptor(s filePath) fileDescGZIP {
 	// Find the descriptor in the v2 registry.
 	var b []byte
 	if fd, _ := protoregistry.GlobalFiles.FindFileByPath(s); fd != nil {
-		if fd, ok := fd.(interface{ ProtoLegacyRawDesc() []byte }); ok {
-			b = fd.ProtoLegacyRawDesc()
-		} else {
-			// TODO: Use protodesc.ToFileDescriptorProto to construct
-			// a descriptorpb.FileDescriptorProto and marshal it.
-			// However, doing so causes the proto package to have a dependency
-			// on descriptorpb, leading to cyclic dependency issues.
-		}
+		b, _ = Marshal(protodesc.ToFileDescriptorProto(fd))
 	}
 
 	// Locally cache the raw descriptor form for the file.
diff --git a/ptypes/any.go b/ptypes/any.go
index e729dcff13..85f9f57365 100644
--- a/ptypes/any.go
+++ b/ptypes/any.go
@@ -19,6 +19,8 @@ const urlPrefix = "type.googleapis.com/"
 
 // AnyMessageName returns the message name contained in an anypb.Any message.
 // Most type assertions should use the Is function instead.
+//
+// Deprecated: Call the any.MessageName method instead.
 func AnyMessageName(any *anypb.Any) (string, error) {
 	name, err := anyMessageName(any)
 	return string(name), err
@@ -38,6 +40,8 @@ func anyMessageName(any *anypb.Any) (protoreflect.FullName, error) {
 }
 
 // MarshalAny marshals the given message m into an anypb.Any message.
+//
+// Deprecated: Call the anypb.New function instead.
 func MarshalAny(m proto.Message) (*anypb.Any, error) {
 	switch dm := m.(type) {
 	case DynamicAny:
@@ -58,6 +62,9 @@ func MarshalAny(m proto.Message) (*anypb.Any, error) {
 // Empty returns a new message of the type specified in an anypb.Any message.
 // It returns protoregistry.NotFound if the corresponding message type could not
 // be resolved in the global registry.
+//
+// Deprecated: Use protoregistry.GlobalTypes.FindMessageByName instead
+// to resolve the message name and create a new instance of it.
 func Empty(any *anypb.Any) (proto.Message, error) {
 	name, err := anyMessageName(any)
 	if err != nil {
@@ -76,6 +83,8 @@ func Empty(any *anypb.Any) (proto.Message, error) {
 //
 // The target message m may be a *DynamicAny message. If the underlying message
 // type could not be resolved, then this returns protoregistry.NotFound.
+//
+// Deprecated: Call the any.UnmarshalTo method instead.
 func UnmarshalAny(any *anypb.Any, m proto.Message) error {
 	if dm, ok := m.(*DynamicAny); ok {
 		if dm.Message == nil {
@@ -100,6 +109,8 @@ func UnmarshalAny(any *anypb.Any, m proto.Message) error {
 }
 
 // Is reports whether the Any message contains a message of the specified type.
+//
+// Deprecated: Call the any.MessageIs method instead.
 func Is(any *anypb.Any, m proto.Message) bool {
 	if any == nil || m == nil {
 		return false
@@ -119,6 +130,9 @@ func Is(any *anypb.Any, m proto.Message) bool {
 //   var x ptypes.DynamicAny
 //   if err := ptypes.UnmarshalAny(a, &x); err != nil { ... }
 //   fmt.Printf("unmarshaled message: %v", x.Message)
+//
+// Deprecated: Use the any.UnmarshalNew method instead to unmarshal
+// the any message contents into a new instance of the underlying message.
 type DynamicAny struct{ proto.Message }
 
 func (m DynamicAny) String() string {
diff --git a/ptypes/doc.go b/ptypes/doc.go
index fb9edd5c62..d3c33259d2 100644
--- a/ptypes/doc.go
+++ b/ptypes/doc.go
@@ -3,4 +3,8 @@
 // license that can be found in the LICENSE file.
 
 // Package ptypes provides functionality for interacting with well-known types.
+//
+// Deprecated: Well-known types have specialized functionality directly
+// injected into the generated packages for each message type.
+// See the deprecation notice for each function for the suggested alternative.
 package ptypes
diff --git a/ptypes/duration.go b/ptypes/duration.go
index 6110ae8a41..b2b55dd851 100644
--- a/ptypes/duration.go
+++ b/ptypes/duration.go
@@ -21,6 +21,8 @@ const (
 
 // Duration converts a durationpb.Duration to a time.Duration.
 // Duration returns an error if dur is invalid or overflows a time.Duration.
+//
+// Deprecated: Call the dur.AsDuration and dur.CheckValid methods instead.
 func Duration(dur *durationpb.Duration) (time.Duration, error) {
 	if err := validateDuration(dur); err != nil {
 		return 0, err
@@ -39,6 +41,8 @@ func Duration(dur *durationpb.Duration) (time.Duration, error) {
 }
 
 // DurationProto converts a time.Duration to a durationpb.Duration.
+//
+// Deprecated: Call the durationpb.New function instead.
 func DurationProto(d time.Duration) *durationpb.Duration {
 	nanos := d.Nanoseconds()
 	secs := nanos / 1e9
diff --git a/ptypes/timestamp.go b/ptypes/timestamp.go
index 026d0d4915..8368a3f70d 100644
--- a/ptypes/timestamp.go
+++ b/ptypes/timestamp.go
@@ -33,6 +33,8 @@ const (
 //
 // A nil Timestamp returns an error. The first return value in that case is
 // undefined.
+//
+// Deprecated: Call the ts.AsTime and ts.CheckValid methods instead.
 func Timestamp(ts *timestamppb.Timestamp) (time.Time, error) {
 	// Don't return the zero value on error, because corresponds to a valid
 	// timestamp. Instead return whatever time.Unix gives us.
@@ -46,6 +48,8 @@ func Timestamp(ts *timestamppb.Timestamp) (time.Time, error) {
 }
 
 // TimestampNow returns a google.protobuf.Timestamp for the current time.
+//
+// Deprecated: Call the timestamppb.Now function instead.
 func TimestampNow() *timestamppb.Timestamp {
 	ts, err := TimestampProto(time.Now())
 	if err != nil {
@@ -56,6 +60,8 @@ func TimestampNow() *timestamppb.Timestamp {
 
 // TimestampProto converts the time.Time to a google.protobuf.Timestamp proto.
 // It returns an error if the resulting Timestamp is invalid.
+//
+// Deprecated: Call the timestamppb.New function instead.
 func TimestampProto(t time.Time) (*timestamppb.Timestamp, error) {
 	ts := &timestamppb.Timestamp{
 		Seconds: t.Unix(),
@@ -69,6 +75,9 @@ func TimestampProto(t time.Time) (*timestamppb.Timestamp, error) {
 
 // TimestampString returns the RFC 3339 string for valid Timestamps.
 // For invalid Timestamps, it returns an error message in parentheses.
+//
+// Deprecated: Call the ts.AsTime method instead,
+// followed by a call to the Format method on the time.Time value.
 func TimestampString(ts *timestamppb.Timestamp) string {
 	t, err := Timestamp(ts)
 	if err != nil {