Frank J. Lapidus is a fictional character on the ABC television series Lost played by Jeff Fahey. Frank is introduced in the second episode of season four as a pilot hired on a mission to the island where Oceanic Flight 815 crashed. He aids the survivors of the crash against mercenary Martin Keamy and helps to rescue a group who become known as the Oceanic Six. Three years later, Frank encounters the group again while working as a commercial airline pilot. His plane lands back on the island, and he is forcibly taken in by a group of his passengers headed by Ilana and Bram, who are working for the island's highest authority figure Jacob. In the series finale, he ultimately escapes the island with a few of his fellow inhabitants.

Lost is an American science fiction adventure drama television series created by Jeffrey Lieber, J. J. Abrams, and Damon Lindelof that aired on ABC from September 22, 2004, to May 23, 2010, over six seasons and 121 episodes. It contains elements of supernatural fiction, and follows the survivors of a commercial jet airliner flying between Sydney and Los Angeles, after the plane crashes on a mysterious island somewhere in the South Pacific Ocean. Episodes typically feature a primary storyline set on the island, augmented by flashback or flashforward sequences which provide additional insight into the involved characters.