His mother was American, while his father was Danish; they met in 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. Lawrence University in Canton, earning a bachelor's degree in Spanish Studies and Politics in 1980.Coincidentally, the play, about homosexual concentration camp prisoners, was originally brought to prominence by Ian Mc Kellen, with whom Mortensen later costarred in The Lord of the Rings.
Two years later, another Cronenberg film, Eastern Promises (2007), earned him further critical acclaim and a nomination for the Academy Award for Best Actor.
A third teaming with Cronenberg in A Dangerous Method (2011) resulted in a nomination for the Golden Globe Award for Best Supporting Actor - Motion Picture.
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.
Mortensen made his first film appearance playing an Amish farmer in Peter Weir's Witness (Mortensen had actually acted in at least one prior film, The Purple Rose of Cairo, but his scenes were deleted from the final cuts).
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, 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. 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. Another major mainstream breakthrough came in 1999, when Peter Jackson cast him as Aragorn in The Lord of the Rings film trilogy. At one point during shooting of The Two Towers, Mortensen, Orlando Bloom, and Brett Beattie (scale 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.
Of these roles, Mortensen was probably best known for playing Master Chief John Urgayle in G. 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. He received critical acclaim for his portrayal of Aragorn, and was ranked No.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." 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 received international attention in the early 2000s with his role as Aragorn in the epic film trilogy The Lord of the Rings.In 2005, Mortensen won critical acclaim for David Cronenberg's crime thriller A History of Violence.15 on a 2015 survey of "The 100 Greatest Movie Characters" conducted by Empire.