O.J. Simpson says he didn't do it ... making a VIDEO claiming he's NOT the real father of Khloe Kardashian -- because he NEVER hooked up with Kris Jenner.
Simpson -- who already shot to 600,000 followers in the 48 hours after joining Twitter -- says he wants to set the record straight on the Kardashian rumors, starting with rumblings that he and Kris got busy back in the day.
"I want to stress ... never in any way shape or form had I ever had any interest in Kris romantically or sexually and I never got any indication that she had any interest in me," Simpson said.
"So, all of these stories are just bogus and bad and tasteless."
Of course, O.J. and Kris' ex-husband, Robert Kardashian, were BFFs -- but O.J. is adamant he never tried to make a move ... even after they divorced.
As for Khloe ... people have been speculating that Simpson is her "real" dad for decades because she looked different than her sisters, Kim and Kourtney.
"Khloe, like all the girls, I'm very proud of," O.J. said ... "just like I know Bob would be if he was here."
"But, the simple facts of the matter is she's not mine."
It's just the tip of the iceberg for Simpson ... who says he has a lot of "getting even" to do on Twitter now that he's learned to use it.