diff --git a/CHANGELOG.md b/CHANGELOG.md
index 18ca302..e5d38e0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ ChangeLog
 ------------------
 
 * This package now supports sabre/event 3.0.
+* The client now sets a default `User-Agent` header identifying this library.
 
 
 4.1.0 (2015-09-04)
diff --git a/lib/Client.php b/lib/Client.php
index 40533fb..0810c4a 100644
--- a/lib/Client.php
+++ b/lib/Client.php
@@ -75,6 +75,7 @@ function __construct() {
             CURLOPT_RETURNTRANSFER => true,
             CURLOPT_HEADER         => true,
             CURLOPT_NOBODY         => false,
+            CURLOPT_USERAGENT      => 'sabre-http/' . Version::VERSION . ' (http://sabre.io/)',
         ];
 
     }
diff --git a/tests/HTTP/ClientTest.php b/tests/HTTP/ClientTest.php
index a9c9f30..ea25907 100644
--- a/tests/HTTP/ClientTest.php
+++ b/tests/HTTP/ClientTest.php
@@ -21,6 +21,7 @@ function testCreateCurlSettingsArrayGET() {
                 CURLOPT_CUSTOMREQUEST  => 'GET',
                 CURLOPT_POSTFIELDS     => '',
                 CURLOPT_PUT            => false,
+                CURLOPT_USERAGENT      => 'sabre-http/' . Version::VERSION . ' (http://sabre.io/)',
             ];
 
         // FIXME: CURLOPT_PROTOCOLS and CURLOPT_REDIR_PROTOCOLS are currently unsupported by HHVM
@@ -50,6 +51,7 @@ function testCreateCurlSettingsArrayHEAD() {
                 CURLOPT_URL            => 'http://example.org/',
                 CURLOPT_POSTFIELDS     => '',
                 CURLOPT_PUT            => false,
+                CURLOPT_USERAGENT      => 'sabre-http/' . Version::VERSION . ' (http://sabre.io/)',
             ];
 
         // FIXME: CURLOPT_PROTOCOLS and CURLOPT_REDIR_PROTOCOLS are currently unsupported by HHVM
@@ -85,6 +87,7 @@ function testCreateCurlSettingsArrayGETAfterHEAD() {
                 CURLOPT_URL            => 'http://example.org/',
                 CURLOPT_POSTFIELDS     => '',
                 CURLOPT_PUT            => false,
+                CURLOPT_USERAGENT      => 'sabre-http/' . Version::VERSION . ' (http://sabre.io/)',
             ];
 
         // FIXME: CURLOPT_PROTOCOLS and CURLOPT_REDIR_PROTOCOLS are currently unsupported by HHVM
@@ -115,6 +118,7 @@ function testCreateCurlSettingsArrayPUTStream() {
                 CURLOPT_CUSTOMREQUEST  => 'PUT',
                 CURLOPT_HTTPHEADER     => ['X-Foo: bar'],
                 CURLOPT_URL            => 'http://example.org/',
+                CURLOPT_USERAGENT      => 'sabre-http/' . Version::VERSION . ' (http://sabre.io/)',
             ];
 
         // FIXME: CURLOPT_PROTOCOLS and CURLOPT_REDIR_PROTOCOLS are currently unsupported by HHVM
@@ -141,6 +145,7 @@ function testCreateCurlSettingsArrayPUTString() {
                 CURLOPT_CUSTOMREQUEST  => 'PUT',
                 CURLOPT_HTTPHEADER     => ['X-Foo: bar'],
                 CURLOPT_URL            => 'http://example.org/',
+                CURLOPT_USERAGENT      => 'sabre-http/' . Version::VERSION . ' (http://sabre.io/)',
             ];
 
         // FIXME: CURLOPT_PROTOCOLS and CURLOPT_REDIR_PROTOCOLS are currently unsupported by HHVM