Mortensen was born in Watertown, New York, on October 20, 1958, the son of Grace Gamble (née Atkinson; July 8, 1928 – April 25, 2015) and Viggo Peter Mortensen Sr. (May 8, 1929 – March 2, 2017). His mother was American, while his father was Danish; they met in Norway. His maternal grandfather was a Canadian from Nova Scotia. One of his grandmothers was from Trondheim, Norway. The family moved to Venezuela, then Denmark, and eventually settled in Argentina in the provinces of Córdoba, Chaco, and Buenos Aires, where Mortensen attended primary school and acquired a fluent proficiency in Spanish while his father managed poultry farms and ranches. He was baptized Lutheran. When Mortensen was 11 and his brothers 8 and 6, their parents divorced and they and their mother returned to the US, where Viggo spent the rest of his childhood in New York, graduating from Watertown High School in Watertown in 1976. He then attended St. Lawrence University in Canton, New York, earning a bachelor’s degree in Spanish studies and politics in 1980. Upon graduating, he lived in England and Spain, then moved back to Denmark, where he took various jobs such as driving trucks in Esbjerg and selling flowers in Copenhagen. He eventually returned to the United States to pursue an acting career.
Mortensen’s first film role was in The Purple Rose of Cairo (1985), but his scenes were deleted from the final cut. His first onscreen appearance was playing an Amish farmer in Peter Weir’s Witness. He was cast in Witness because the director thought he had the right face for the part of an Amish man. He had also been simultaneously cast for another role as a soldier in Shakespeare in the Park’s production of Henry V, but he decided to turn down that one for the film because he wanted to try something new. He credited that decision and the very positive experience on the film as the start of his film career. Also in 1985, he was cast in the role of Bragg on Search for Tomorrow. Mortensen’s 1987 performance in Bent at the Coast Playhouse, Los Angeles, won him a Dramalogue Critics’ Award. The play, about homosexual concentration camp prisoners, was originally brought to prominence by Ian McKellen, with whom Mortensen later costarred in The Lord of the Rings. In 1987, Mortensen guest starred as a police detective on the hit series Miami Vice. During the 1990s, Mortensen appeared in supporting roles in a variety of films, including Jane Campion’s The Portrait of a Lady, Young Guns II, Prison, Boiling Point, Leatherface: The Texas Chainsaw Massacre III, Sean Penn’s The Indian Runner, Danny Cannon’s The Young Americans, Carl Colpaert’s The Crew, which won the São Paulo Film Festival Audience Award, Brian de Palma’s Carlito’s Way, Crimson Tide, G.I. Jane, Daylight, A Walk on the Moon, American Yakuza, Charles Robert Carner’s remake Vanishing Point, Philip Ridley’s films The Reflecting Skin and The Passion of Darkly Noon, the remake films A Perfect Murder and Gus Van Sant’s Psycho (the 1998 remakes of two Alfred Hitchcock’s movies Dial M for Murder and Psycho), 28 Days, and The Prophecy, with Christopher Walken. Of these roles, Mortensen was probably best known for playing Master Chief John Urgayle in G.I. Jane. Another major mainstream breakthrough came in 1999, when Peter Jackson cast him as Aragorn in The Lord of the Rings film trilogy. According to the Special Extended Edition DVD of The Lord of the Rings: The Fellowship of the Ring, Mortensen was a last-minute replacement for Stuart Townsend, and would not have taken the part of Aragorn had it not been for his son’s enthusiasm for the J. R. R. Tolkien novel. In The Two Towers DVD extras, the film’s swordmaster, Bob Anderson, described Mortensen as “the best swordsman I’ve ever trained.” Mortensen often performed his own stunts, and even the injuries he sustained during several of them did not dampen his enthusiasm. At one point during shooting of The Two Towers, Mortensen, Orlando Bloom, and Brett Beattie (stunt double for John Rhys-Davies) all had painful injuries, and during a shoot of them, running in the mountains, Peter Jackson jokingly referred to the three as “the walking wounded.” Also, according to the Special Extended Edition DVD of The Lord of the Rings: The Return of the King, Mortensen purchased the two horses, Uraeus and Kenny, whom he rode and bonded with over the duration of the films. He received critical acclaim for his portrayal of Aragorn, and was ranked No. 15 on a 2015 survey of “The 100 Greatest Movie Characters” conducted by Empire. In 2004, Mortensen starred as Frank Hopkins in Hidalgo, the story of an ex-army courier who travels to Arabia to compete with his horse, Hidalgo, in a dangerous desert race for a contest prize. In 2005, Mortensen starred in David Cronenberg’s movie A History of Violence as a family man revealed to have had an unsavory previous career. He was nominated for a Satellite Award for Outstanding Actor in a Motion Picture for this role. In the DVD extras for A History of Violence, Cronenberg related that Mortensen is the only actor he had come across who would come back from weekends with his family with items he had bought to use as props on the set. In 2006, he starred as Captain Diego Alatriste in the Spanish language film Alatriste, based on the series of novels The Adventures of Captain Alatriste, written by the Spanish writer Arturo Pérez-Reverte. In September 2007, the film Eastern Promises, directed by David Cronenberg, was released to critical acclaim for the film itself and for Mortensen’s performance as a Russian gangster on the rise in London. His nude fight scene in a steam room was applauded by Roger Ebert: “Years from now, it will be referred to as a benchmark.” Mortensen’s performance in Eastern Promises resulted in his winning the Best Performance by an Actor in a British Independent Film award from the British Independent Film Awards. He was also nominated for an Academy Award for Best Actor. In 2009, Mortensen appeared as himself in the film Reclaiming The Blade, in which he discussed his passion for the sword and his sword-work in films such as The Lord of the Rings and Alatriste. Mortensen also talked about his work with Bob Anderson, the swordmaster on The Lord of the Rings, Alatriste, Pirates of the Caribbean and many others. In 2009, Mortensen performed in The People Speak, a documentary feature film that uses dramatic and musical performances of the letters, diaries, and speeches of everyday Americans, based on historian Howard Zinn’s A People’s History of the United States. While it was reported in April 2009 that Mortensen had, at least temporarily, retired from film acting, Mortensen said he was misquoted. In a 2012 interview, he denied that he ever said he was retiring, only that he didn’t have “plans to do another movie” at the time and that he was “taking a little break now. I don’t have anything lined up.” In 2009 he joined the cast of The Road, a film adaptation of the Cormac McCarthy novel of the same name, and collaborated with David Cronenberg for a third time on A Dangerous Method. After two years, Mortensen returned to theater in 2011, starring in Ariel Dorfman’s Purgatorio in Madrid. Mortensen starred in the 2016 film Captain Fantastic and the 2018 film Green Book, for which he received his second and third Academy Award nominations.
With part of his earnings from The Lord of the Rings, Mortensen founded the Perceval Press publishing house—named after the knight from the legend of King Arthur—to help other artists by publishing works that might not find a home in more traditional publishing venues. Perceval Press is also the home of Mortensen’s many personal artistic projects in the area of fine arts, photography, poetry, song, and literature (see below).