Who was the only Best Actor Oscar winner who was in his 70s when he won?

Answer 1

Henry Fonda

Henry Fonda was 76 years old when he won the Best Actor Oscar for On Golden Pond (1981), his sole Oscar. The other three closest winners in age were George Arliss (for Disraeli (1929/30)), John Wayne (for True Grit (1969)), and Paul Newman (for The Color of Money (1986)) - all at 62 years of age with their sole Oscar wins.