A Quick One is the second studio album by the English rock band the Who, released on 9 December 1966. In the United States, where the song "Happy Jack" was a top 40 hit, the album was released in April 1967 under the title Happy Jack with a slightly altered track listing.

Unlike other albums by the Who, where guitarist Pete Townshend was the primary or sole songwriter, A Quick One features significant songwriting contributions from all band members, with lead vocalist Roger Daltrey contributing one song, bassist John Entwistle and drummer Keith Moon each contributing two. The album also included a cover of the Holland–Dozier–Holland song "Heat Wave" and ends with a musical suite titled "A Quick One, While He's Away", which served as an inspiration for later rock operas that the Who would become known for.