Hello Mary Lou: Prom Night II is a 1987 Canadian supernatural slasher film directed by Bruce Pittman, written by Ron Oliver, and starring Michael Ironside, Wendy Lyon, Louis Ferreira, and Lisa Schrage. It follows a high school student who becomes possessed by Mary Lou Maloney, a student who died at her high school prom in 1957. A sequel to the slasher film Prom Night (1980), it was originally intended to be a standalone film titled The Haunting of Hamilton High, but was retitled in order to capitalize on the success of the original Prom Night. The only story connection between the two films is that they are set at the same high school. Both films were executive produced by Peter R. Simpson.

Filmed in Edmonton, Alberta in 1986, the film was retitled Hello Mary Lou: Prom Night II by its Canadian distributor, Alliance Films. It was released theatrically in the United States by The Samuel Goldwyn Company in October 1987, and grossed nearly $3 million at the U.S. box office. The film received mixed reviews from critics, with many drawing stylistic comparisons to various other films of the era, ranging from David Lynch's Blue Velvet to its horror contemporaries Carrie and A Nightmare on Elm Street.

The character Mary Lou Maloney would also appear in the next installment, Prom Night III: The Last Kiss (1990).