Boomtown (also known as Boomtown Fair) is a British music festival held annually on the Matterley Estate in South Downs National Park, near Winchester, Hampshire. It was first held in 2009 and has been held at its current site since 2011. Its diverse line-up of bands, DJs and speakers perform on many different stages each a part of a district with its own individual theme. Each yearly event is known as a Chapter and expands on the story line from the previous year, told through the sets, live actors and many forms of alternate reality games. The festival site is split into several districts, and the narrative is reflected in the design of the districts, streets and venues, which are populated by hundreds of actors to play the role of inhabitants. The large scale of the sets and infrastructure require six weeks of construction, and a month of disassembly.

The event is centered around a set of common beliefs and principles, mainly supporting the progressive ideas of environmentalism and social equality, as set out in its vision code, The Six Pillars of Boomtown