Justin Bieber vs. Lady Gaga


Social media is one way to measure the popularity of a celebrity... and now there's a new top dog!

Justin Bieber surpassed fellow singer Lady Gaga Monday night to become the most-followed person on Twitter.

Both have more than 33.3 million followers, but Bieber is just a little bit ahead of Gaga now.

Neither immediately acknowledged the milestone.

Gaga held the top spot since August 2010, when she overtook another well known singer... Britney Spears.