Mobile Fidelity Sound Lab (MFSL or MoFi) is a company that produces reissues of albums. All releases are made from the first generation master tape and mastered at half-speed, which MFSL claims allows for an improved sound quality. In the past, MFSL has produced cassette tapes, LPs, CDs, and VHS releases of a few titles. In addition, each title is licensed to be mastered, manufactured, and sold within a specific time frame with limited quantities produced.

Although Mobile Fidelity existed prior to 1978, MFSL's popularity began at that time with the Original Master Recording LP. The first titles in the series were classical releases by the Mystic Moods Orchestra. The label hit mainstream appeal with their release of Supertramp's Crime of the Century. Other popular titles followed, such as Steely Dan's Katy Lied, George Benson's Breezin', Fleetwood Mac's S/T, and Pink Floyd's Dark Side of the Moon.

MFSL's releases became highly publicized in 1981 when they released a box set of Beatles recordings. This comprised all thirteen original British versions of their albums, mastered from the original Abbey Road Studio master tapes with the exception of Magical Mystery Tour which was sourced from the original US Capitol tapes. The releases used high-density "virgin" vinyl and half-speed mastering. An album-sized booklet displaying the original album covers was also included. The box set was followed up with box sets of Frank Sinatra and The Rolling Stones.