Justin Bieber jacked a bicycle from a security guard in a Vegas casino ... AND GOT CAUGHT BY A COUPLE OF GIANT GOONS ... and TMZ has footage of the entire botched heist.
It all went down at The Palms Casino Resort on September 14 ... when JB and his crew were in town to watch the Floyd Mayweather fight.
Bieber entered the building through an employee entrance and stumbled upon a patrol bicycle in the hallway -- so, he took it.
Security footage shows Justin joyriding the bike through the halls -- while a security guard chased after him in an effort to get the bike back.
Eventually, a couple of bigger security guys -- dressed in suits (so you know they're not f**kin around) -- cornered Justin in the hallway and forced the pop star to hand over the stolen property.
We're told security gave Justin a stern talking to and eventually let him go.