Bieber has challenged Cruise to a fight in the Octagon, the home of UFC fighting.
"I wanna challenge Tom Cruise to fight in the octagon.
"Tom if you dont take this fight your scared and you will never live it down," he posted on social media.
"Who is willing to put on the fight?" Bieber asked, before tagging in the president of the UFC Dana White.
Neither Cruise nor White have responded yet to the bizarre request from Bieber.
And there's been no explicit reason given for why Bieber chose to target Cruise.
But Conor McGregor's already offered to host the fight.
"If Tom Cruise is man enough to accept this challenge, McGregor Sports and Entertainment will host the bout. Does Cruise have the sprouts to fight, like he does in the movies?" McGregor tweeted.
It's not the first time Bieber has issued "challenges" on social media.
He's previously issued a friendly ice hockey challenge to fellow singer Shawn Mendes after the There's Nothing Holdin' Me Back hitmaker was declared the "Prince of Pop".
Bieber couldn't resist the urge to tease his fellow Canadian over the "Prince of Pop" headline.
"Hmm Gonna have to break a few more records to dethrone my title there bud," he commented under the photo. "but if you want we can play hockey for it..."