Victor Ortiz: Floyd Mayweather's Knockout Was "Totally Unfair"

Victor Ortiz tells TMZ, Floyd Mayweather screwed him out of a fair fight -- catching him completely off-guard with a sucker punch ... and now he wants a rematch.

Victor hit up The Ivy in Bev Hills yesterday -- and told us, he only put his hands down because he was waiting for the ref's signal ... and Floyd clocked him with a "totally unfair" left hook.