He returned to Broadway portraying Professor Henry Higgins in My Fair Lady (1956) where he won the Tony Award for Best Actor in a Musical.

Receiving critical acclaim for his performance in Major Barbara (1941), which was shot in London during the Blitz, his roles since then included Blithe Spirit (1945), Anna and the King of Siam (1946), The Ghost and Mrs. Muir (1947), Cleopatra (1963), My Fair Lady (1964), reprising his stage role as Henry Higgins which won him an Academy Award for Best Actor, and the titular character in Doctor Dolittle (1967).

[3] He was the youngest of three children and had two older sisters, Edith Marjorie Harrison (1900-1976) and Sylvia Sackville, Countess De La Warr, DBE (1903-1992).

His West End debut in the same year was in Terence Rattigan's French Without Tears which proved to be his breakthrough stage role as a leading light comedian.

[3] His acting career was interrupted by World War II, during which he served in the Royal Air Force (1942–1944), reaching the rank of Flight Lieutenant.

[6] 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 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 had support roles in Get Your Man (1934), Leave It to Blanche (1934), and All at Sea (1935), and a better part in Men Are Not Gods (1936) as a reporter in love with Miriam Hopkins; this was the first time Harrison worked for Alexander Korda.

Harrison had a key support role in The Citadel (1938) for MGM and starred in a comedy for Korda, Over the Moon (1939) alongside Merle Oberon.

Harrison played Adolphus in Major Barbara (1941)—filmed in London during The Blitz of 1940, a role for which he received critical acclaim, and a success at the British box office.

[6] Harrison returned to films as the lead in Blithe Spirit (1945), from the play by Noël Coward, directed by David Lean.

Harrison received an offer from Joseph L. Mankiewicz to play Julius Caesar in the 20th Century Fox epic Cleopatra (1963).

He was one of several stars in the popular The Yellow Rolls-Royce (1964), and played the Pope opposite Charlton Heston in Fox's The Agony and the Ecstasy (1965), for Carol Reed.

Harrison made two more films for 20th Century Fox, both expensive play adaptations that failed at the box office: A Flea in Her Ear (1968), and Staircase (1969).

[18] After a break from screen acting, Harrison appeared in The Prince and The Pauper (1977) and a Hindi film, Shalimar, alongside Indian Bollywood stars Dharmendra and Zeenat Aman.

His physique and looks were far more striking once middle age had literally stretched too smooth and callow a youthful face into a long, saturnine physiognomy, whose hooded eyes and wide mouth had satyr-like associations for some people.

In 1942, he divorced his first wife, Noel Margery Colette Thomas, and married actress Lilli Palmer the next year; they later appeared together in numerous plays and films, including The Four Poster.

[21] Harrison's involvement in the scandal by waiting several hours before calling a doctor and police[22] briefly damaged his career and his contract with Fox was ended by mutual consent.

[28] In 1980, despite his having married twice since their divorce, Roberts made a final attempt to win Harrison back, which proved to be futile; she took her own life that same year.

Harrison's sister Sylvia was married to the 1st Earl of Kilmuir (better known to history as Sir David Maxwell Fyfe), a lawyer, Conservative politician and judge who was successively the lead British prosecutor at Nuremberg, Home Secretary and Lord Chancellor (head of the English judiciary); after his death she married another Cabinet minister, the 9th Earl De La Warr.

Seth MacFarlane, creator of the animated series Family Guy, modelled the voice of the character Stewie Griffin after Harrison, after seeing him in the film adaptation of My Fair Lady.

[54][55] Ex-CIA chief of disguise Jonna Mendez stated in 2019 that a mask of Harrison was used by multiple CIA agents for covert work.

[56] According to Mendez, Rex Harrison's aluminium facial props mould was used as a baseline for over-the-head masks that the agency would create and use operationally.