Update: Selena Gomez won this round. Click here to vote for her Selenators!

In Round 1 of March Madness, Selena Gomez's Selenators are battling it out against Ariana Grande's Arianators for the title of Best Fanbase. Which group has your vote?

Selena Gomez's fans have been devoted to the singer and actress ever since she first won our hearts on Wizards of Waverly Place. Whether Sel is shaking things up on the big screen (like in Spring Breakers) or crooning incredibly heartfelt tunes like "The Heart Wants What It Wants," Selenators have staunchly supported their idol through it all. And of course, Selena pays it back in big ways, even going so far as to reach out to a suicidal fan in the hopes to save her life. Truly amazing.

Like Selenators, Ariana Grande's Arianators know a thing or two about loyalty -- after all, they've been with her ever since she was a redhead on Victorious. Of course, once her music career took off, the fanbase exploded exponentially -- and it's not hard to see why (Ari is crazy talented, of course!) Arianators have supported their idol through everything from the devastating death of her beloved grandpa to the wild success of her sophomore album, My Everything, which has since gone platinum.

You can vote for Selenators or Arianators once per hour until the poll closes on March 17 at 3PM ET. The winner of this round will go on to compete against a different fanbase in Round 2 and be one step closer to winning it all. Happy voting!

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