Windows Live Messenger is an instant messaging client for Windows XP, Windows Server 2003, Windows Vista, and Windows Mobile, first released on December 13, 2005 by Microsoft. blank">Windows Live Messenger release dates from official blog It is the successor to _MSN Messenger. It is part of Microsoft's Windows Live set of online services. The current version is Windows Live Messenger 8.5, which was released on November 6, 2007.

The client connects to Microsoft's .NET Messenger Service. Corporations can also integrate their Live Communication Server and Active Directory with the network on behalf of its clients. Most major multi-protocol clients can also connect to the service.