Adam "Pacman" Jones will be back behind bars again ... TMZ Sports has learned he's just been sentenced to jail for his role in a huge bar fight earlier this year.
As we previously reported, the former NFL star was at Clutch OTR in Cincinnati, Ohio on Feb. 15 ... when law enforcement claims the dude snapped on venue staffers.
Authorities say Jones got into a wild brawl with the establishment's employees -- claiming the ex-football player knocked out a bouncer during the fracas.