Justin Bieber may have a massive following around the world and a pop superstar status, but "Harry Potter" star Daniel Radcliffe admits that he knew very little about him.

The 20-year-old British actor knew Bieber was a singer but has mistaken the 'Baby' hitmaker for a woman, claiming "I genuinely thought it was a woman singing."

"I only heard Justin Bieber for the first time two weeks ago. I genuinely thought it was a woman singing." He continued, "I'd never heard it before. Is it big in England yet? I'm so out of the loop when it comes to pop culture that I kind of don't even try anymore," Radcliffe said in a recent interview with MTV News.

Bieber has not yet given any response on his comment.

Meanwhile, Radcliffe knew who Lady Gaga was and even called her "amazing."

"She's really got a voice. My god. Not my kind of music particularly but she can really sing," he said.

For now, Radcliffe will have to manage a hectic schedule ahead of him. Beside reprising his role as young wizard Harry Potter in "Harry Potter and the Deathly Hallows: Part I" and "Harry Potter and the Deathly Hallows: Part II", he is also making his Broadway return on "How to Succeed in Business Without Really Trying" which will be run in the spring of 2011.