I Know What You Did Last Summer is a 1997 American slasher film based on the 1973 novel of the same name by Lois Duncan. The film stars Jennifer Love Hewitt, Sarah Michelle Gellar, Ryan Phillippe and Freddie Prinze Jr., with Anne Heche and Bridgette Wilson appearing in supporting roles. It centers on four friends who are being stalked by a killer, one year after covering up a car accident in which they were involved. The film was directed by Jim Gillespie, from a screenplay written by Kevin Williamson, writer of Scream. The film was followed by three sequels, I Still Know What You Did Last Summer (1998), the straight-to-DVD release I'll Always Know What You Did Last Summer (2006), and the legacy sequel also titled I Know What You Did Last Summer (2025).