U.K. were a British progressive rock supergroup originally active from 1977 to 1980. The band was founded by bass guitarist John Wetton and drummer Bill Bruford, formerly the rhythm section of King Crimson. The band was rounded out by violinist/keyboardist Eddie Jobson, and guitarist Allan Holdsworth. Bruford and Holdsworth left in 1978, and Bruford was replaced by drummer Terry Bozzio. Jobson, Wetton and Bozzio reformed U.K. for a world tour in 2012.

Progressive rock is a broad genre of rock music that primarily developed in the United Kingdom through the mid- to late 1960s, peaking in the early 1970s. Initially termed "progressive pop", the style was an emergence of psychedelic bands who abandoned standard pop traditions in favour of instrumentation and compositional techniques more frequently associated with jazz, folk, or classical music. Additional elements contributed to its "progressive" label: lyrics were more poetic, technology was harnessed for new sounds, music approached the condition of "art", and the studio, rather than the stage, became the focus of musical activity, which often involved creating music for listening rather than dancing.