Usher is hopping aboard Kim Kardashian's undergarment train -- he's just the most recent star to partner up with her and promote her SKIMS line ... and yeah, he's shirtless for it.
Kim and co. were able to get Usher to agree to be the newest face for their SKIMS Men's campaign -- and they got him to rock their underwear line for fellas ... including their SKIMS Stretch collection as well as their SKIMS Cotton collection.
As part of this new drop featuring Usher .