What Lies Beneath is a 2000 American supernatural thriller film directed by Robert Zemeckis from a screenplay by Clark Gregg, who co-wrote the story with Sarah Kernochan. The film stars Harrison Ford as a university professor and Michelle Pfeiffer as his wife, who is unsure if their home is haunted by a ghost or if she is losing her mind. The film also features Diana Scarwid in a supporting role.

The first film 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.

What Lies Beneath 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.