The Adventures of Elmo in Grouchland (or simply Elmo in Grouchland) is a 1999 American musical adventure comedy film directed by Gary Halvorson (in his feature directorial debut) from a screenplay written by Mitchell Kriegman and Joey Mazzarino, based on a story conceived by Kriegman. This was the second of the two theatrical feature films to be based on the children's television series Sesame Street, after Sesame Street Presents: Follow That Bird in 1985. It stars Mandy Patinkin and Vanessa Williams alongside Muppet performers Kevin Clash, Caroll Spinney, Steve Whitmire, and Frank Oz. It features songs written by a wide range of songwriters, including Siedah Garrett, Jeff Elmassian, Andy Rehfeldt, Martin Erskine, Seth Friedman, and Michael & Patty Silversher, with a score composed and conducted by John Debney.

Produced by Jim Henson Pictures and Children's Television Workshop, the film was released by Columbia Pictures on October 1, 1999. The film received generally positive reviews from critics, but was a box-office disappointment, grossing $12 million against a budget of more than $26 million.

The film was one of the few Sesame Street productions directly produced by The Jim Henson Company. This was the final Muppet feature film to involve Fran Brill and Oz, who retired from being full-time puppeteers the following years, and the last Muppet film to feature Spinney before his retirement in 2018 and his death in 2019.