William Reibert Mapother, Jr. (; born April 17, 1965) is an American actor. He is best known for his role as Ethan Rom on the television series Lost.

Early life
Mapother was born in Louisville, Kentucky. He is the son of Louisa (née Riehm) and William Reibert Mapother, Sr. He is of English, Irish, and mostly German ancestry.

He is a first cousin of actor Tom Cruise, whose real name is Thomas Cruise Mapother IV. Mapother has appeared in five movies starring Cruise. He had tiny roles in Minority Report and Vanilla Sky, and supporting roles in Mission: Impossible II, Born on the Fourth of July and Magnolia. Mapother has two sisters, Katherine and Amy. His father was a lawyer and judge in Louisville, between 1967 and 1970. His father died on June 22, 2006.

Mapother graduated from the University of Notre Dame. He majored in English. Then, he taught high school in East Los Angeles for three years before becoming an actor.

Career
Mapother has become widely known as a character actor. He sometimes plays scary or otherwise dark characters. He played an important role in Todd Field's In the Bedroom. Mapother is more widely known as Ethan Rom in the TV show Lost. The character was killed early in the first season. Since then, however, he has appeared in seven episodes mainly through flashbacks, once due to time travel and another in an alternate timeline. In total, he appeared in eleven episodes of Lost.

Mapother has also had major roles in several independent movies, such as The Lather Effect, Moola, Hurt and  Another Earth. Mapother starred in The Burrowers as a Native American 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.

Television and movie roles
 American Horror Story (TV, 1 episode, 2012) .... Misogynist Driver
 Justified (TV, 2 episodes, 2012) .... Delroy Baker
 The Mentalist (TV, 2 episodes, 2011-2013) .... Richard Haibach
 Edwin Boyd: Citizen Gangster (2011) .... Detective Rhys
 Warrior (2011) .... David Milligan
 Another Earth (2011) .... John Burroughs
 A Warrior's Heart (2010)
 Hurt (2008) .... Darryl Coltrane
 Prison Break (TV, 2 episodes, 2009) .... FBI Agent Chris Franco
 Lost (TV, 11 episodes, 2004–2010) .... Ethan Rom
 Criminal Minds (TV, 1 episode, 2008) .... Ian Corbin
 The Burrowers (Film, 2008) .... Will Parcher
 Lost: Missing Pieces (TV, 1 episode, 2008) .... Ethan Rom
 Skip Tracer (TV, 2008) .... Henry Hargrove Jr.
 WordGirl (TV animation, 2007) ... Guy Rich (voice)
 Viva Laughlin (TV, 1 episode, 2007) .... Sweet Lenny Collins
 K-Ville (TV, 1 episode, 2007) .... Gordon Wix
 Moving McAllister (2007) .... Bob
 Moola (2007) .... Steve
 Robot Chicken (TV, 2 episodes, 2006) .... Alien Bully / Leprechaun #2
 World Trade Center (2006) .... Jason Thomas
 The Lather Effect (2006) .... Jack
 Ask The Dust (2006) .... Bill
 Crossing Jordan (TV, 1 episode, 2005) .... Henry Bishop
 Threshold (TV, 2 episodes, 2005) .... Gunneson
 Chloe (2005) .... Doctor
 The Zodiac (2005) .... Dale Coverling
 Lords of Dogtown (2005) .... Donnie
 The Inside (TV, 1 episode, 2005) .... Ronald Ewing
 The Grudge (2004) .... Matthew Williams
 NCIS (TV, 1 episode, 2004) .... Kyle Grayson
 CSI: Miami (TV, 1 episode, 2004) .... Pete Keller
 Suspect Zero (2004) .... Bill Grieves
 Line of Fire (TV, 2 episodes, 2004) .... Larry
 The Kiss (2003) .... Peter
 Touched by an Angel (TV, 2 episodes, 2003) .... Eddie
 Law & Order: Special Victims Unit (TV, 1 episode, 2003) .... Luke Edmunds
 The Pennsylvania Miners' Story (TV, 2002) .... John 'Flathead' Phillippi
 CSI: Crime Scene Investigation (TV, 1 episode, 2002) .... Douglas Sampson
 Self Storage (2002) .... Graham
 Minority Report (2002) .... Hotel Clerk
 Swordfish (2001) .... Gabriel's Crew
 In the Bedroom (2001) .... Richard Strout
 Almost Famous (Scenes Deleted, 2000) .... Bartender
 Mission: Impossible II (2000) .... Wallis
 Magnolia (1999) .... WDKK Show Director's Assistant
 The Unknown Cyclist (1998) .... By-Stander
 Trickle (1998) .... Josh Riddell
 Without Limits (1998) .... Bob Peters
 Born on the Fourth of July (1989) .... Platoon Member – Vietnam

References

1965 births
Living people
American television actors
Actors from Louisville, Kentucky
American movie actors