Microsoft Lumia is a discontinued line of mobile devices that was originally designed and marketed by Nokia and later by Microsoft Mobile. Introduced in November 2011, the line was the result of a long-term partnership between Nokia and Microsoft—as such, Lumia smartphones run on Microsoft software, the Windows Phone operating system; and later the newer Windows 10 Mobile. The Lumia name is derived from the partitive plural form of the Finnish word lumi, meaning "snow".

Microsoft Mobile Oy was a subsidiary of Microsoft involved in the development and manufacturing of mobile phones. Based in Espoo, Finland, it was established in 2014 following the acquisition of Nokia's Devices and Services division by Microsoft in a deal valued at €5.4 billion, which was completed in April 2014. Nokia's then-CEO, Stephen Elop, joined Microsoft as president of its Devices division following the acquisition, and the acquisition was part of Steve Ballmer's strategy to turn Microsoft into a "devices and services" company. Under a 10-year licensing agreement, Microsoft Mobile held rights to sell feature phones running the S30/S30+ platform under the Nokia brand.