Floyd Mayweather -- Hijacked By Hasselhoff!!

With Floyd Mayweather running seriously behind for his big media event at his Vegas boxing gym, there was another huge star who took over the spotlight ... DAVID HASSELHOFF!!

Hoff was swarmed by the horde of reporters who came from all over the world for the event ... and told the media he was totally fired up for the big fight.

Unclear why Hoff hit up the gym ... it's like 2 miles from the strip -- so it's not like he just strolled on over.