According to the British television channel ITV, the English actress beat competition from Scarlett Johansson and Judy Garland to be named a film favourite.
A survey of starlets was conducted by Yahoo! Entertainment. The poll of 1600 movie-goers revealed that some of the stars from the golden age of Hollywood can still shine today.
Judy Garland, who starred in The Wizard of Oz, came in second place, followed by Scarlett Johansson in third.
Knightley, 21, has already earned an Oscar nomination for her role of Elizabeth Bennet in the film Pride and Prejudice. Actresses Natalie Portman, Lindsay Lohan, Brooke Shields and Mia Farrow also appeared on the list.