In fact, there are some – even showbiz types – who are unaware of the teen pop phenom.
"I only heard Justin Bieber for the first time, like, two weeks ago," Daniel Radcliffe recently told MTV News.
And when he did, the Harry Potter star was in for a surprise.
"I genuinely thought it was a woman singing. I'd never heard it before," the Brit, 20, says, laughing.
One star, however, who has caught Radcliffe's attention: Lady Gaga. "I think she's kind of amazing. She's really got a voice. My god, you know?" he says, before admitting that her style isn't quite "my kind of music particularly."
Still, says Radcliffe, "she can really sing."