Steven Seagal nearly ended Luke Rockhold's fighting career earlier this year -- when he executed his legendary "death touch" on the UFC fighter ... who admits, "He put me on notice!!!"
Rockhold -- who's fighting Lyoto Machida at "UFC Fight Night" Saturday -- told us all about the run in with Seagal in Vegas back in January ... where he got straight up OWNED!
FYI -- Seagal is no joke, the guy is a real life martial arts expert -- a 7th-dan black belt in Aikido.
Check out the pic below -- you can tell by Luke's face, he wasn't messin' around!!!