Emlyn Williams was born George Emlyn Williams on 26 November 1905 at Pen-y-ffordd, near Mostyn in Flintshire, into a Welsh-speaking working-class family. He spoke only Welsh until the age of eight. A teacher at his grammar school in Holywell, Sarah Grace Cooke, took a close interest in his education, helping him perfect his French in France and later win a scholarship to Christ Church, Oxford. Miss Cooke later became the model for the schoolteacher in Williams' best-known play, The Corn Is Green, which drew heavily on his own childhood in north Wales.
Williams became an overnight stage sensation in 1935 with Night Must Fall, a thriller in which he wrote and played the lead role of a baby-faced murderer, praised for its unusually deep psychological portrait of a killer for its time. He followed it in 1938 with The Corn Is Green, which went on to be staged on Broadway with Ethel Barrymore, filmed in 1945 with Bette Davis, and revived many times since, including at the National Theatre in London in 2022.
Alongside his stage work, Williams built a long screen career, acting in films such as The Citadel (1938), Alfred Hitchcock's Jamaica Inn (1939), Major Barbara (1941) and Ivanhoe (1952), and playing the Roman emperor Caligula in the unfinished 1937 production of I, Claudius. In 1949 he wrote, directed and starred in The Last Days of Dolwyn, a film shot in Wales that marked the screen debut of a young actor he had spotted at an audition in Cardiff: Richard Burton. The two remained close, and Williams later became godfather to Burton's daughter, the actress Kate Burton.
Williams was appointed CBE in 1962 and received an honorary degree from the University of Wales in 1949. In his later years he toured the world with acclaimed one-man shows built around readings from Charles Dickens, Dylan Thomas and Saki.