William Reibert Mapother, Jr. (pronounced /ˈmeɪpɒθɚ/; born April 17, 1965) is an American actor and former teacher, perhaps best known for his role as Ethan Rom on the television series Lost.
Mapother was born in Louisville, Kentucky, the son of Louisa and William Reibert Mapother, Sr. He is a first cousin of actor Tom Cruise (as his father and Cruise's father were siblings). Mapother had a cameo role in Minority Report opposite Cruise. He has two sisters, Katherine and Amy (an occasional actress, born February 17, 1974), both born in Louisville, Kentucky. His father was an attorney and bankruptcy consultant and was a judge in Louisville between 1967 and 1970; William Reibert, Sr. died on June 22, 2006 after fighting lung cancer and pulmonary fibrosis.
Mapother graduated from the University of Notre Dame as an English major, and then taught high school in East Los Angeles for three years before becoming an actor. He completed a Church of Scientology course in 1989. However, unlike his cousin he has since then not followed through on the course.
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 five episodes through flashbacks. This brings the total amount of episodes he appeared in up to nine.
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.
In September 2007 he was elected to a three-year term on the National Board of Directors for the Screen Actors Guild.
