A King must be many things: Bright, bold and quick on his feet. And, in the case of the PopCrush crowd, he must be under 21.

Now that we've crowned Lady Gaga and Harry Styles as our official emblems of summertime, we're looking to outfit our kingdom with a brand new King and Queen. Across the next few weeks, we'll pit some of entertainment's most glistering stars against each other in a series of heats, until only two remain, who will assume a pair of official PopCrush thrones. And our tournament's first male duel features a pair of social media stars who have battled their ways into the big leagues.

The 17-year-old Shawn Mendes first caught the eyes of record executives with his Vine performances, and has since carved out a verifiable music career, including the Billboard No. 1 release of his debut album, Handwritten in AprilHe's got a Teen Choice award, gone on tour with Austin Mahone and is opening select tour dates for Taylor Swift along the 1989 route. Royal material?

Troye Sivan, who's 20, has amassed more than 3.7 million YouTube subscribers, and also snatched up a Teen Choice award for his collaboration with Tyler Oakley. Plus, he's got a full-length album, Wild, on the way, and was recently featured on Zedd's latest, "Papercut." Is he most suited to occupy your dream castle?

Which one of these young gentlemen has what it takes to reign over Young Hollywood? Cast your vote in the poll, explain your choice in the comments and check back soon to see who'll take one big step out of serfdom!

We'll reveal the winner of this round on August 24 at 5 PM. Get to voting! And if you haven't yet, place your votes in the other rounds for King of Young Hollywood.

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