Who was the only Best Actress Oscar winner who was in her 50s when she won?

Answer 1

Shirley Booth

Shirley Booth was 54 years old when she won the Best Actress Oscar for Come Back, Little ShebaGuess Who's Coming to Dinner (1967)), and both Susan Sarandon (for Dead Man Walking (1995)) and Shirley MacLaine (for Terms of Endearment (1983)) were 49 years old when they won.