Windows Phone 8.1 Update 1 (or just Windows Phone 8.1 Update) is one of two planned OS updates to the Microsoft Windows Phone 8.1 operating system. The update is known internally as GDR1 or general distribution release 1 and contains many OS fixes, improvements and support for new hardware for manufacturers.

GDR updates are similar to service packs on the Windows desktop OS and comes in between major OS milestones. The last GDR update was in December 2013 known as Windows Phone 8 Update 3. Later, in spring 2014, Windows Phone 8.1 was released to manufacturers and the Preview for Developers program.

Consumer facing features include support for native Folder creation on the Start screen, interactive phone covers and numerous minor tweaks, including some improved core experiences. Many details about GDR1 were revealed on July 26 and July 27 when OEM information about the update leaked on Microsoft's developer portal website.

Windows Phone 8.1 Update 1 finished development in July 2014 and users part of the Preview for Developers Program are expected to receive the bits for the software in August 2014. General rollout to phones through an over-the-air update should begin by September.