Boxing fans want to see Jake Paul take on a "real" challenge after beating Mike Tyson ... and well, they might get their wish -- 'cause heavyweight champion Daniel Dubois just called him out for a fight.
The 27-year-old IBF title holder extended the offer to El Gallo ... saying, "Hi Jake, good business on the weekend but how would you feel fighting for the legitimate heavyweight championship of the world this is Daniel Dubois calling you out.