Mike Tyson says he thinks Brad Pitt is a "really nice guy" -- which is interesting considering he once caught the guy about to have sex with his estranged wife.
Iron Mike was on "The Real" when he was asked to recall that infamous moment back in the '80s when he caught his then (estranged) wife Robin Givens sneaking around their house with Pitt.
The whole thing is funny ... Tyson says he was actually at the house hoping to bang Givens one last time before they hashed it out with divorce lawyers when he saw Robin with Brad.