Harrison was born at Derry House in Huyton, Merseyside, the son of Edith Mary (née Carey) and William Reginald Harrison, a cotton broker. He was educated at Liverpool College. After a bout of childhood measles, Harrison lost most of the sight in his left eye, which on one occasion caused some on-stage difficulty. He first appeared on the stage in 1924 in Liverpool. Harrison’s acting career was interrupted during World War II while serving in the Royal Air Force, reaching the rank of Flight Lieutenant. He acted in various stage productions until 11 May 1990. He acted in the West End of London when he was young, appearing in the Terence Rattigan play French Without Tears, which proved to be his breakthrough role.

He alternated appearances in London and New York in such plays as Bell, Book and Candle (1950), Venus Observed, The Cocktail Party, The Kingfisher and The Love of Four Colonels, which he also directed. He won his first Tony Award for his appearance as Henry VIII in Anne of the Thousand Days and international superstardom (and a second Tony Award) for his portrayal of Henry Higgins in the musical My Fair Lady, where he appeared opposite Julie Andrews.

Later appearances included Pirandello’s Henry IV, a 1984 appearance at the Haymarket Theatre with Claudette Colbert in Frederick Lonsdale’s Aren’t We All?, and one on Broadway at the Brooks Atkinson Theatre presented by Douglas Urbanski, at the Haymarket in J.M. Barrie’s The Admirable Crichton with Edward Fox. He returned as Henry Higgins in the revival of My Fair Lady directed by Patrick Garland in 1981, cementing his association with the plays of George Bernard Shaw, which included a Tony nominated performance as Shotover in Heartbreak House, Julius Caesar in Caesar and Cleopatra, and General Burgoyne in a Los Angeles production of The Devil’s Disciple.

Harrison’s film debut was in The Great Game (1930), other notable early films include The Citadel (1938), Night Train to Munich (1940), Major Barbara (1941), Blithe Spirit (1945), Anna and the King of Siam (1946), The Ghost and Mrs. Muir (1947), and The Foxes of Harrow (1947). He was best known for his portrayal of Professor Henry Higgins in the 1964 film version of My Fair Lady based on the Broadway production of the same name, which was based on George Bernard Shaw’s play Pygmalion) for which Harrison won a Best Actor Oscar.

He also starred in 1967’s Doctor Dolittle. At the height of his box office clout after the success of My Fair Lady, Harrison proved a domineering and demanding force during production, demanding auditions for prospective composers after musical playwright Leslie Bricusse was contracted and demanding to have his singing recorded live during shooting, only to agree to have it rerecorded in post-production. He also disrupted production with incidents with his wife, Rachel Roberts and deliberate misbehaviour, such as when he deliberately moved his yacht in front of cameras during shooting in St. Lucia and refused to move it out of sight due to contract disputes. Harrison was at one point temporarily replaced by Christopher Plummer, until he agreed to be more cooperative.

He starred in the 1968 comedy The Honey Pot, a modern adaptation of Ben Jonson’s play Volpone. Two of his co-stars, Maggie Smith and Cliff Robertson, were to become lifelong friends. Both spoke at his New York City memorial at the Little Church Around the Corner when Harrison died in 1990.  Harrison was not by any objective standards a singer (his talking on pitch style he used in My Fair Lady would be adopted by many other classically trained actors with limited vocal ranges); the music was usually written to allow for long periods of recitative, or “speaking to the music.” Nevertheless, “Talk to the Animals”, which Harrison performed in Doctor Dolittle, won the Academy Award for Best Original Song in 1967.

Despite excelling in comedy (Noël Coward described him as “The best light comedy actor in the world—except for me.”) he attracted favourable notices in dramatic roles such as his portrayal of Julius Caesar in Cleopatra (1963) and as Pope Julius II in The Agony and the Ecstasy (1965), opposite Charlton Heston as Michelangelo. He also acted in a Hindi film Shalimar alongside Indian Bollywood star Dharmendra as well as appearing as an aging homosexual man opposite Richard Burton as his lover in Staircase (1969).

Harrison was married six times. In 1942, he divorced his first wife, Colette Thomas, and married actress Lilli Palmer the next year; the two later appeared together in numerous plays and films, including The Fourposter.  In 1947, while married to Palmer, Harrison began an affair with actress Carole Landis. Landis committed suicide in 1948 after spending the evening with Harrison. Harrison’s involvement in the scandal by waiting several hours before calling a doctor and police briefly damaged his career and his contract with Fox was ended by mutual consent.

1957 Harrison married the actress Kay Kendall. Kendall died of Myeloid leukemia in 1959. Terence Rattigan’s 1973 play In Praise of Love was written about the end of this marriage, with Harrison appearing in the New York production playing the character based on himself. Rattigan was said to be “intensely disappointed and frustrated” by Harrison’s performance, as “Harrison refused to play the outwardly boorish parts of the character and instead played him as charming throughout, signalling to the audience from the start that he knew the truth about [the] illness.” Critics however were quite pleased with the performance and although it did not have a long run, it was yet another of Harrison’s well plotted naturalistic performances.  He was subsequently married to Welsh-born actress Rachel Roberts from 1962 to 1971. After a final attempt to win Harrison back proved futile, Roberts committed suicide in 1980.

Harrison then married Elizabeth Rees-Williams, divorcing in 1975, and finally in 1978, Mercia Tinker, who would become his sixth and final wife. Harrison’s eldest son Noel Harrison became an olympic skier, singer and occasional actor; he toured in several productions including My Fair Lady in his father’s award-winning role. Noel died suddenly of a heart attack on 19 October 2013 at age 79. His younger son Carey Harrison is a playwright and social activist.

Having retired from films after the 1982 picture A Time to Die, Harrison continued to act on Broadway and the West End until the end of his life, despite suffering from glaucoma, painful teeth, and a failing memory. He was nominated for a third Tony Award in 1984 for his performance as Captain Shotover in the revival of George Bernard Shaw’s Heartbreak House. He followed the show up with two successful pairings with Claudette Colbert, The Kingfisher in 1985, and Aren’t We All? in 1986. In 1989, he appeared with Edward Fox in The Admirable Crichton in London. In 1989-1990, he appeared on Broadway in The Circle by W. Somerset Maugham, opposite Glynis Johns and Stewart Granger. The production actually opened at Duke University for a three-week run followed by performances in Baltimore and Boston before opening 14 November 1989 on Broadway.

Harrison died of pancreatic cancer at his home in Manhattan on 2 June 1990 at the age of 82. He had only been diagnosed with the disease for a short time. The stage production in which he was appearing at the time, The Circle, came to an end upon his death.  Harrison’s second autobiography, A Damned Serious Business: My Life in Comedy, was published posthumously in 1991.