Ethan Rom is a fictional character portrayed by William Mapother on the ABC television show Lost. Introduced in the first season as the main antagonist, Ethan is the surgeon for the antagonistic and mysterious group known as the "Others". He infiltrated the fuselage survivors, posing as one of them until they discovered his true identity. He then kidnapped Charlie Pace and the pregnant Claire Littleton, attempting to dispose of the former soon after. Ethan is one of the few characters to have more episode appearances while his character was dead rather than alive. Ethan is one of few people known to have been born on the island, as seen in the ninth episode of the fifth season, "Namaste".

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.