William Reibert Mapother, Jr.

William Reibert Mapother, Jr. is an American actor and former teacher, known for his role as Ethan Rom on the television series Lost. He is actor Tom Cruise's cousin as his father and Cruise's father were brothers.

After graduating from the University of Notre Dame as an English major, he taught high school in East Los Angeles for three years before becoming an actor. He completed a Church of Scientology course in 1989.

He has appeared in four movies starring Cruise; a cameo role in Minority Report and supporting roles in Mission: Impossible II, Born of the Fourth of July, and Magnolia. Mapother has two sisters, Katherine and Amy, both born in Louisville, Kentucky. His father was an attorney, bankruptcy consultant and judge in Louisville, between 1967 and 1970; William Reibert, Sr., died on June 22, 2006, after fighting lung cancer and pulmonary fibrosis.

Mapother has become widely known as a character actor, who sometimes plays scary or otherwise dark characters. Despite playing a pivotal role in Todd Field's In the Bedroom, Mapother is perhaps more widely known as Ethan Rom in the TV show Lost. The character was killed off early in the first season, but since then has appeared in seven episodes mainly through flashbacks, once due to time travel and another in an alternate timeline. This brings the total amount of Lost episodes he appeared in up to eleven.

In addition, Mapother has also had considerable roles in a series of independent films, such as The Lather Effect, Moola and the upcoming Hurt, in which he stars alongside Melora Walters as the 'reclusive' brother-in-law of Walters' character. Mapother starred in The Burrowers as a former Indian fighter who joins a posse to help find missing white settlers, only to discover that the hunters have become the hunted.

In September 2007 he was elected to a three-year term on the National Board of Directors for the Screen Actors Guild.