Born in New York City. Leading man of the 1940s turned veteran Hollywood character player. O'Brien joined Orson Welles's Mercury Players in 1937 and worked in film and on stage through the 1940s, turning primarily to the screen after WW II. He is best remembered as the lead in the noir classic, D.O.A. (1950) and for his role as a sycophantic Hollywood press agent in THE BAREFOOT CONTESSA (1954). He also excelled at broad comedy, witness his turn as a weight-sensitive gangster in 1956's THE GIRL CAN'T HELP IT. He kept a high profile in solid supporting roles in BIRDMAN OF ALCATRAZ, THE MAN WHO SHOT LIBERTY VALENCE (both 1962), SEVEN DAYS IN MAY (1964, for which he picked up another Oscar nomination), and THE WILD BUNCH (1969). Having starred on radio in the title role of "Yours Truly, Johnny Dollar" (one of several actors to play that part), he went on to topline such TV series as "Johnny Midnight" (1960), "Sam Benedict" (1962-63), and "The Long Hot Summer" (1965-66), and appear in numerous series episodes and telefilms, but his latter-day feature films were unmemorable. His last movie was 1980's DREAM NO EVIL. Some of his other memorable films include: 1939: THE HUNCHBACK OF NOTRE DAME; 1943: THE AMAZING MRS. HOLLIDAY; 1944: WINGED VICTORY; 1947: A DOUBLE LIFE; 1948: ANOTHER PART OF THE FOREST, AN ACT OF MURDER, FIGHTER SQUADRON 1949: WHITE HEAT 1950: 711 OCEAN DRIVE, THE ADMIRAL WAS A LADY 1951: SILVER CITY 1952: THE DENVER AND THE RIO GRANDE, THE TURNING POINT; 1953: MAN IN THE DARK, JULIUS CAESAR (as Casca); 1954: SHIELD FOR MURDER (which he codirected), PETE KELLY'S BLUES; 1956: 1984, THE RACK; 1957: THE BIG LAND 1958: SING BOY SING; 1959: UP PERISCOPE; 1960: THE LAST VOYAGE, THE GREAT IMPOSTOR; 1961: MAN-TRAP; (which he directed and coproduced); 1962: THE LONGEST DAY; 1964: RIO CONCHOS; 1965: SYLVIA, SYNANON; 1972: THEY ONLY KILL THEIR MASTERS; 1974: LUCKY LUCIANO. His brother was screenwriter Liam O'Brien. O'Brien was married to actresses Nancy Kelly (1941-1942) and Olga San Juan (1948-1976); Maria O'Brien, his daughter by the latter, has appeared in several films. O'Brien died of Alzheimer's disease in 1985.  Supporting Actor 1954: THE BAREFOOT CONTESSA  Nominated for Supporting Actor 1964: SEVEN DAYS IN MAY 2 nominations, 1 Award