I Know What You Did Last Summer (1997)

I Know What You Did Last Summer is a 1997 American slasher film starring Jennifer Love Hewitt, Sarah Michelle Gellar, Ryan Phillippe, and Freddie Prinze Jr. as four teenage friends who are stalked by a hook-wielding killer one year after covering up a car accident in which they supposedly killed a man. It was directed by Jim Gillespie and written by Kevin Williamson, who adapted the 1973 novel. It is the first in the I Know What You Did Last Summer film series.

Williamson was approached to adapt Lois Duncan's source novel by producer Erik Feig. Where Scream, released the previous year, contained prominent elements of satire and self-referentiality, Williamson's script for I Know What You Did Last Summer reworked the novel's central plot to resemble a straightforward 1980s-era slasher film.

I Know What You Did Last Summer was released theatrically in the United States on October 17, 1997 by Columbia Pictures. It received a mixed reception from critics and grossed $125 million on a budget of $17 million. The film was parodied in Scary Movie (2000) and is frequently referenced in popular culture, as well as being credited alongside Scream with revitalizing the slasher genre in the 1990s.

The film was followed by three sequels – I Still Know What You Did Last Summer (1998), I'll Always Know What You Did Last Summer (2006) and I Know What You Did Last Summer (2025) – and a 2021 television series.