Quitting (Chinese: 昨天; lit. 'Yesterday') is a 2001 Chinese drama film directed by Zhang Yang, starring and based on the true life story of Jia Hongsheng. Jia, an actor and former drug addict, battled his addiction to marijuana and heroin for five years from 1992 to 1997. All members of the cast, from Jia and Jia's family members right down to the doctors and patients at a mental institute Jia was admitted to, are real people playing themselves. The film premiered at the Venice Film Festival on 4 September 2001 and clinched the NETPAC Award.

The original Chinese title is an allusion to the Beatles' 1965 classic song "Yesterday". References to The Beatles, of whom Jia was an avid fan, are also made throughout the film. Besides dressing up like John Lennon, Jia also fantasized himself as Lennon's son and recited the Chinese translation of the lyrics to Let It Be religiously. However, Michael Jackson, who owned the rights to most Beatles songs, declined to give permission for the song or its title to be used in the film. Instead, the film uses songs by Chinese rockers such as Cui Jian, Tang Dynasty and Dou Wei.