Knowles was selected by the readers of the internet site AskMen. The 25 year-old star was given the majority of the 8.5 million votes.
Readers were asked to base their decision on sex appeal, beauty, intelligence, humour, charisma and ambition.
Knowles, who stars in the Oscar-nominated film Dreamgirls, beat competition from actresses Scarlett Johansson and Jessica Alba, supermodel Adriana Lima and actress Jessica Biel.