George Coulouris was born to a Greek immigrant father, a merchant, and an English mother. He was educated at Manchester Grammar School in England. As an actor, he was skilled at playing both villains and nobler roles. He was a member of Orson Welles' Mercury Theater players and appeared in films such as Citizen Kane, For Whom the Bell Tolls, Papillon, and Murder on the Orient Express.
Coulouris studied at London's Central School of Speech and Drama under Elsie Fogerty. He made his London stage debut in 1925 with Henry V at the Old Vic. He soon played the Yank in the first British production of Eugene O'Neill's The Hairy Ape. By 1929, he had reached Broadway, starring in a modern dress version of Measure for Measure.
His breakthrough role came when he played Tallant in The Late Christopher Bean, which led to a Hollywood contract with MGM in 1933. He met Orson Welles during this time and joined Welles' Mercury Theatre, playing Mark Antony in a modern dress production of Julius Caesar in 1937. When Welles went to Hollywood to make Citizen Kane, Coulouris played the role of Walter Parks Thatcher, the Kane family's lawyer and business manager.
Coulouris continued to work in Hollywood throughout the 1940s, playing character parts in a string of films. He returned to England in the late 1940s and joined the Bristol Old Vic, where he starred in Tartuffe and later transferred to London. In the 1950s and 1960s, he remained a prominent stage actor, taking on roles in productions such as An Enemy of the People, The Plough and the Stars, Altona, The Dance of Death, and Cat on a Hot Tin Roof.
Despite his film reputation, Coulouris' stage work was often overshadowed by his film appearances. He tended to play mundane roles in British films, but rose to the occasion in roles such as Babalatchi in Outcast of the Islands and Big Daddy in Cat on a Hot Tin Roof. Toward the end of his life, he turned to writing and produced charming memoirs about his early life and stage experiences.