Superstar is a 1999 American comedy film and a Saturday Night Live spin-off about a quirky, socially inept girl named Mary Katherine Gallagher. The character was created by SNL star Molly Shannon and appeared as a recurring character on SNL in numerous skits. The story follows Mary Katherine trying to find her place in her Roman Catholic private school. The movie is directed by former Kids in the Hall member Bruce McCulloch. It stars Molly Shannon, Will Ferrell, Elaine Hendrix, Harland Williams, Mark McKinney, who appeared in many of the Mary Katherine Gallagher SNL skits on TV, and Glynis Johns in her final film. Molly Shannon received a nomination for Blockbuster Entertainment Award "Favorite Actress - Comedy" but lost out to Heather Graham in Austin Powers: The Spy Who Shagged Me.

Mary Katherine Gallagher is a fictional character invented and portrayed by Saturday Night Live cast member Molly Shannon from 1995 to 2001. She was considered the first breakout character from the new 1995 cast and a significant marker of the increased influence of women writers on the show in the 1990s. Shannon portrayed the character in a 1999 film, Superstar, and she also reprised the role when she hosted Saturday Night Live in 2007. Shannon first created an early version of the character when she was in school at NYU, during a comedy show directed by Madeleine Olnek.