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

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.