Why was Audrey Hepburn's performance in Roman Holiday a breakthrough role?

Audrey Hepburn’s performance in the 1953 film Roman Holiday was a breakthrough role because it marked her first major American film appearance and immediately established her as a significant talent in Hollywood.123

In the film, directed by William Wyler, Hepburn portrayed a princess who escapes her royal duties to explore Rome. Critics and audiences were captivated by her unique ability to combine a regal bearing with a tomboyish winsomeness, a quality that projected both sophistication and charming innocence. This performance was so well-received that it earned her an Academy Award for best actress, launching her career as one of the most iconic stars in screen history.32