The actress, who is married to heartthrob Ryan Reynolds, was fascinated by the pop star as a teenager, reported Contactmusic.
"My teen idol was Britney Spears. My prom dress looked like something she'd have worn - powder pink and with a bare midriff. I had to wear flat shoes with it, as my date was so short," Lively said.
While the stunning star is known for her stylish outfit choices, she has a favourite era for fashion and dreams of re-visiting the period and wearing the classic pieces.