I Know What You Did Last Summer is a 1997 American slasher film written by Kevin Williamson and directed by Jim Gillespie. The film is loosely based on the 1973 novel of the same name by Lois Duncan. The film also draws inspiration from the urban legend known as The Hook.
The film stars Jennifer Love Hewitt, Sarah Michelle Gellar, Ryan Phillippe and Freddie Prinze, Jr., with Anne Heche, Bridgette Wilson, and Johnny Galecki appearing in supporting roles. I Know What You Did Last Summer centers on four friends who are being stalked by a killer, one year after covering up a car accident in which they were involved.
I Know What You Did Last Summer received mixed reviews from critics, but was commercially successful, grossing over $125 million at the box office. It was also nominated for and won multiple awards. As a result, the film has been parodied and referenced in popular culture.
The film was followed by two sequels, I Still Know What You Did Last Summer (1998) and the straight-to-DVD release I'll Always Know What You Did Last Summer (2006). Though the former film sees a continuation of the plotline established in its predecessor, the latter film establishes a new plotline and does not star any cast members from the previous two installments.