Humpday is a 2009 American mumblecore comedy-drama film directed, produced, and written by Lynn Shelton and starring Mark Duplass, Joshua Leonard, and Alycia Delmore. It premiered at the 2009 Sundance Film Festival. International distribution rights were purchased by Magnolia Pictures for a mid-six figure sum. The film opened in New York City in a limited release on July 10, 2009. The story line follows two male heterosexual best friends, Ben and Andrew. The plot line centers around a "mutual dare" that is introduced at a party, which involves the two main characters engaging in a pornographic film together. The film was shot on-location in Washington state around Seattle from September 2008 to January 2009, and much of the dialogue for the film was improvised.

Humpday received positive critical reception and won the Special Jury Prize for Spirit of Independence at the 2009 Sundance Film Festival, among other awards.

In 2012, a remake in French entitled Do Not Disturb was released.