Joey Chestnut -- DEFEATED AGAIN ... Stonie Crushes Champ At Rib Cook-Off

Might finally be time to stick a fork in Joey Chestnut, 'cause after tasting defeat at the Hot Dog championships ... the eating legend has now lost at RIBS as well.

FYI -- Chestnut was the reigning rib champion at the annual Rib Cook-Off at the Nugget in Sparks, Nevada ... "was" being the operative word, thanks to his arch enemy Matt Stonie.

Stonie ate like a MONSTER Wednesday night -- throwing down 10.5 POUNDS of ribs in 12 minutes. Chestnut only sucked down 9.75 pounds, good enough for 2nd place.

It's been a rough year for Joey -- after losing his crown at Nathan's Hot Dog eating championships on July 4th ... and even breaking off his engagement to his GF earlier this year.

Let's not take away from Stonie's accomplishments though -- his numbers are good ... and at 23 years old, he seems to be the future of gluttony.