The Hangover Part II is a 2011 American comedy film produced by Legendary Pictures and distributed by Warner Bros. Pictures. The sequel to the 2009 film The Hangover and the second installment in The Hangover trilogy, the film was directed by Todd Phillips, who co-wrote the script with Craig Mazin and Scot Armstrong, and stars Bradley Cooper, Ed Helms, Zach Galifianakis, Ken Jeong, Jeffrey Tambor, Justin Bartha, and Paul Giamatti.

It tells the story of Phil, Stu, Alan, and Doug, as they travel to Thailand. After the bachelor party in Las Vegas, Stu takes no chances and opts for a safe, subdued pre-wedding brunch. Things do not go as planned, resulting in another bad hangover with no memories of the previous night.

Development began in April 2009, two months before The Hangover was released. The principal actors were cast in March 2010 to reprise their roles from the first film. Production began in October 2010, in Ontario, California, before moving on location in Thailand. The film was released on May 26, 2011, and became the eighth-highest-grossing film of 2011 and the highest-grossing R-rated comedy during its theatrical run, but unlike the first film, The Hangover Part II received mixed reviews.

A third installment, The Hangover Part III, was released on May 23, 2013.