Randy Orton's tattoo artist is suing WWE and 2K Games -- the company behind WWE 2K18 -- claiming they used her designs without permission.

The woman behind the suit is Catherine Alexander -- a tattoo artist from Illinois -- who says she's been tattooing Orton going back to '03 ... and owns the copyrights to the designs.

Problem is, according to Alexander, Orton is depicted in the video games to a tee -- tattoos included -- and she says that's copyright infringement.

The artists claims she raised the issue with WWE in 2009 ... and was offered $450 for the rights to use the designs.

She says she declined the offer. 

As for the tats in question ... Alexander says she gave Orton a tribal tattoo on his upper back ... as well as full sleeve with everything from a Bible verse to a dove, skulls and a rose ... among others.

FYI -- this ain't the first time we've seen a suit like this ... LeBron James' tattoo artist sued 2K last year ... making a similar claim.

It's unclear exactly how much money Alexander is after ... but the game's a massive success ... we're guessing it's a lot more than WWE allegedly offered her the first time.