An American gymnast has stunned the world with a flawless floor routine which left judges gobsmacked.

Katelyn Ohashi, who currently competes for the University of California, received a perfect score of 10 after she wowed the crowd at the Collegiate Challenge with a routine soundtracked by hits such as September, I Want You Back and The Way You Make Me Feel.

A video of the 2018 NCAA co-champion's performance has since gone viral on social media, with more than 1.5 million views on Twitter.

One user deemed it "the most exciting floor routine they had ever seen" while another hailed Ohashi's routine as "mind-bending".

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UCLA head coach Valorie Kondos Field was in awe of Ohashi after the routine.

"I've never seen her facial, her performance quality, be that professional as I saw tonight," Kondos Field told the Los Angeles Times.

"Her whole floor routine is ridiculously hard. Every single thing about it including the backwards split that she does after her leap pass – it's insane.

"I said to myself, 'Okay, she's back'. And when I went to hug her afterwards, she goes 'I'm back."

The UCLA gymnastics team took first place over the University of Nebraska-Lincoln.