diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 48c5e3e..536961f 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -28,9 +28,9 @@ This library uses [semantic versioning](http://semver.org/). For each release, t
 1. Make sure the tests are passing in CI for the branch you're building
 2. Create a new branch for the release, for example `release/1.2.3`
 3. Update the CHANGELOG.md with any customer-affecting changes since the last release and add this to the git index
-4. Replace all references of the current version number with the new version number and add this to the git index
+4. Set the `VERSION` constant in `version.go` to the new version number and add this to the git index
 5. Create a PR for the release branch
 6. Once the PR is approved, merge it into `main`
-7. Run `git tag <VERSION_NUMBER>` with the new version and push the tag to git
+7. Add a tag and push to origin - e.g.: `git tag v1.2.3` && `git push origin v1.2.3`
 8. Create the release on Github, from the new tag, including populating the release notes
 9. Update the [Ably Changelog](https://changelog.ably.com/) (via [headwayapp](https://headwayapp.co/)) with these changes (again, you can just copy the notes you added to the CHANGELOG)
diff --git a/client.go b/client.go
index 5c10ef1..44c89a1 100644
--- a/client.go
+++ b/client.go
@@ -20,6 +20,7 @@ package control
 import (
 	"bytes"
 	"encoding/json"
+	"fmt"
 	"io"
 	"net/http"
 )
@@ -27,12 +28,20 @@ import (
 // The URL of the Ably Control API.
 const API_URL = "https://control.ably.net/v1"
 
+// defaultAblyAgent is the default value to set as the Ably-Agent HTTP header,
+// and can be extended for an individual Client by calling the AppendAblyAgent
+// method.
+const defaultAblyAgent = "ably-control-go/" + VERSION
+
 // Client represents a REST client for the Ably Control API.
 type Client struct {
 	token     string
 	accountID string
 	// Url is the base url for the REST API.
 	Url string
+
+	/// ablyAgent is the value to set as the Ably-Agent HTTP header.
+	ablyAgent string
 }
 
 // NewClient creates a new REST client.
@@ -46,8 +55,9 @@ func NewClient(token string) (Client, Me, error) {
 // / NewClientWithURL is the same as NewClient but also takes a custom url.
 func NewClientWithURL(token, url string) (Client, Me, error) {
 	client := Client{
-		token: token,
-		Url:   url,
+		token:     token,
+		Url:       url,
+		ablyAgent: defaultAblyAgent,
 	}
 	me, err := client.Me()
 	if err != nil {
@@ -57,6 +67,12 @@ func NewClientWithURL(token, url string) (Client, Me, error) {
 	return client, me, nil
 }
 
+// AppendAblyAgent appends an extra entry to the value sent as the Ably-Agent
+// HTTP header.
+func (c *Client) AppendAblyAgent(product, version string) {
+	c.ablyAgent = fmt.Sprintf("%s %s/%s", c.ablyAgent, product, version)
+}
+
 func (c *Client) request(method, path string, in, out interface{}) error {
 	var inR io.Reader
 	if in != nil {
@@ -71,6 +87,7 @@ func (c *Client) request(method, path string, in, out interface{}) error {
 		return err
 	}
 	req.Header.Set("Authorization", "Bearer "+c.token)
+	req.Header.Set("Ably-Agent", c.ablyAgent)
 	if in != nil {
 		req.Header.Set("Content-Type", "application/json")
 	}
diff --git a/client_test.go b/client_test.go
index 1662746..7a9bfc5 100644
--- a/client_test.go
+++ b/client_test.go
@@ -3,6 +3,8 @@ package control
 import (
 	"fmt"
 	"math/rand"
+	"net/http"
+	"net/http/httptest"
 	"os"
 	"testing"
 	"time"
@@ -65,3 +67,33 @@ func newTestClient(t *testing.T) (Client, Me) {
 	return client, me
 
 }
+
+// TestAblyAgent tests that client requests set the Ably-Agent HTTP header.
+func TestAblyAgent(t *testing.T) {
+	// start a test HTTP server which tracks the value of the Ably-Agent
+	// HTTP header and returns an empty JSON object.
+	var ablyAgent string
+	handler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		ablyAgent = req.Header.Get("Ably-Agent")
+		w.Header().Set("Content-Type", "application/json")
+		w.Header().Set("Content-Length", "2")
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("{}"))
+	})
+	srv := httptest.NewServer(handler)
+
+	// initialise a client, which will make a request to /me
+	client, _, err := NewClientWithURL("s3cr3t", srv.URL)
+	assert.NoError(t, err)
+
+	// check the Ably-Agent HTTP header was set
+	assert.Equal(t, "ably-control-go/"+VERSION, ablyAgent)
+
+	// add an extra Ably-Agent entry
+	client.AppendAblyAgent("test", "1.2.3")
+
+	// check requests now set the updated Ably-Agent HTTP header
+	_, err = client.Me()
+	assert.NoError(t, err)
+	assert.Equal(t, "ably-control-go/"+VERSION+" test/1.2.3", ablyAgent)
+}
diff --git a/version.go b/version.go
new file mode 100644
index 0000000..f64f73b
--- /dev/null
+++ b/version.go
@@ -0,0 +1,6 @@
+package control
+
+// VERSION is the version of this package.
+//
+// It is sent in requests to the Control API in the Ably-Agent HTTP header.
+const VERSION = "0.1.0"