Early life
Donat was born in Withington, Manchester, Lancashire, to Ernst Emil Donat and his wife Rose Alice (née Green) who were married at Withington's St Paul's Church, in 1895. He was of English, Polish, German and French descent and was educated at Manchester's Central High School for Boys.

Donat had a brother, John Donat, who was a trapper in Canada and later moved to Shelton, Connecticut, USA. John Donat's children were Jean, Jay and Peter. He was the owner of Lake George Camp for Girls in Gull Bay, New York, which catered to old New York families.

Career
Donat made his first stage appearance in 1921, at the age of 16, with Henry Baynton's company at the Prince of Wales Theatre, Birmingham, playing Lucius in Julius Caesar. His real break came in 1924 when he joined the company of Shakespearean actor Sir Frank Benson, where he stayed for four years. Donat made his film debut in 1932 in Men of Tomorrow. His first great screen success came with The Private Life of Henry VIII, playing Thomas Culpeper.

He had a successful screen image as an English gentleman who was neither haughty nor common. That made him something of a novelty in British films at the time, and he was likened by critics to Hollywood's Clark Gable and Gary Cooper. His most successful films included The Ghost Goes West (1935), Hitchcock's The 39 Steps (1935), The Citadel (1938), for which he received his first Best Actor Oscar nomination, and Goodbye, Mr. Chips (1939). The last saw him win the Academy Award for Best Actor, over Clark Gable for Gone with the Wind, Laurence Olivier for Wuthering Heights, James Stewart for Mr. Smith Goes to Washington and Mickey Rooney for Babes in Arms. He was a major theatre star, noted for his performances on the British stage in Shaw's The Devil's Disciple (1938) and Heartbreak House (1942), Much Ado About Nothing (1946) and especially as Thomas Becket in T.S. Eliot's Murder in the Cathedral at the Old Vic Theatre (1952).

Donat lobbied hard to be cast in two film roles, neither of which he gained. He wanted to play the Chorus in Olivier's Henry V, but the role went to Leslie Banks, and he longed desperately to be cast against type as Bill Sikes in David Lean's Oliver Twist, but Lean thought him wrong for the part and cast Robert Newton instead.

According to Judy Garland in an interview, although she first sang "You Made Me Love You" for Clark Gable, she was disappointed because she really had wanted to sing it for her idol Donat, to whom she wrote a fan letter after seeing The Count of Monte Cristo (1934).