Ramón Gerard Antonio Estévez (born August 3, 1940), known professionally as Martin Sheen, is an American actor. Born and raised in the United States by immigrant parents of Irish and Spanish ancestry. He underwent a quadruple heart bypass operation in December 2015.

Sheen married Janet Templeton[60] on December 23, 1961, and they have four children, three sons and a daughter, all of whom are actors: Emilio, Ramón, Carlos, and Renée. Carlos, however, decided to change his name when he began acting, calling himself Charlie Sheen. He celebrated his 50th wedding anniversary in 2011.

Although he did not attend college, Sheen credited the Marianists at University of Dayton as a major influence on his public activism, as well as Archbishop Desmond Tutu. Sheen is known for his outspoken support of liberal political causes, such as opposition to United States military actions and a hazardous-waste incinerator in East Liverpool, Ohio.

He supported the 1965 farm worker movement with Cesar Chavez in Delano, California. Sheen is a follower of the Consistent life ethic, which opposes abortion, euthanasia, capital punishment and war. He articulated this view further in an interview with The Progressive: "I'm inclined to be against abortion of any life. But I am equally against the death penalty or war." He also stated at the same occasion: "I personally am opposed to abortion, but I will not judge anybody else's right in that regard because I am not a woman and I could never face the actual reality of it." He also supports the Democrats for Life of America's Pregnant Women Support Act.

In early 2003 Sheen signed the "Not in My Name" declaration opposing the invasion of Iraq (along with prominent figures such as Noam Chomsky and Susan Sarandon); the declaration appeared in the magazine The Nation. On August 28, 2005, he visited Camp Casey to pray with anti-Iraq War activist Cindy Sheehan, who had demanded a second meeting with U.S. President George W. Bush.

In a speech at Oxford University in 2009, Sheen stated that he had been arrested 66 times for protesting and acts of civil disobedience.[76] He was described by human rights activist Craig Kielburger as having "a rap sheet almost as long as his list of film credits."[77]

On April 1, 2007, Sheen was arrested, with 38 other activists, for trespassing at the Nevada Test Site at a Nevada Desert Experience event protesting against the site.[78]

He has a long association with Sea Shepherd and that conservation organization has named a ship, the RV Martin Sheen to recognize his commitment and support.