What Lies Beneath is a 2000 American supernatural horror thriller film directed by Robert Zemeckis and starring Harrison Ford and Michelle Pfeiffer, with supporting performances from Diana Scarwid, Miranda Otto, James Remar, Joe Morton, and Amber Valletta. Its plot focuses on a woman (Pfeiffer) who comes to suspect that the lakeside Vermont home she shares with her husband (Ford) is haunted by a female ghost.

The original story for What Lies Beneath was written by Sarah Kernochan, inspired by a real paranormal experience she had. The project began development around 1998, with Clark Gregg making several alterations to Kernochan's original treatment, which he eventually developed into a feature-length screenplay. Principal photography took place on location in Vermont and on soundstages in Los Angeles, while director Zemeckis was taking a hiatus from filming his concurrent project, Cast Away (2000). It was the first film produced by Zemeckis' production company ImageMovers.

What Lies Beneath was theatrically released in North America by DreamWorks Pictures and internationally by 20th Century Fox on July 21, 2000. While it received mixed reviews from critics who praised Pfeiffer's performance and criticized Gregg's script, the film was a box office success, grossing US$291 million worldwide and becoming the tenth highest-grossing film of the year.

The film was nominated for the Saturn Award for Best Horror Film at the 27th Saturn Awards, in addition to nominations for Best Director (for Zemeckis) and Best Actress (for Pfeiffer). At the 7th Blockbuster Entertainment Awards, Ford and Pfeiffer won Favorite Actor – Suspense and Favorite Actress – Suspense, respectively, and Scarwid was nominated for Favorite Supporting Actress – Suspense.