Windows Live Messenger（简写WLM，俗称MSN），是微软开发的即时通信软件，现已结束服务。8.0版本之前称作MSN Messenger。预载于窗口操作系统之中，是微软在线服务Windows Live的一部分，Windows Live Messenger包括MSN Messenger的全部功能，并再加上新的连接和共享文档方法，例如支持了MSN Messenger所不支持的离线消息以及离线共享文档。同时，微软也从Windows Live OneCare中提取出一个杀毒组件，专供Windows Live Messenger用于扫描接收到的文档。

Windows Live Messenger (formerly MSN Messenger) is a discontinued instant messaging client developed by Microsoft for Windows, Xbox 360, BlackBerry OS, iOS, Java ME, S60 on Symbian OS 9.x, and Zune HD. It connected to the Microsoft Messenger service while also having compatibility with Yahoo! Messenger and Facebook Messenger. The client was first released as MSN Messenger on July 22, 1999, and was marketed under the MSN branding until 2005 when it was rebranded under Windows Live and has since been officially known by its present name, although its previous name was still used colloquially by most of its users. In June 2009, Microsoft reported the service attracted over 330 million active users each month, placing Messenger among the most widely used instant messaging clients in the world.