'The Bachelorette' Contestant – Hospitalized After Brutal 'Gang' Brawl

JJ Lane -- one of the so-called 'Brokeback Bachelors' from this season of “The Bachelorette” -- got ambushed by a gang of dudes waiting outside a cast and crew after-party.

The beatdown happened Saturday night when JJ was leaving the "Men Tell All" after-party. Production sources tell us he and a crew member got jumped by a group of at least 5 thugs.

It got ugly, real quick -- we're told JJ and the crew member took a few shots to the face, and the brawl continued until someone ran into the club to grab fellow contestant Ben Zorn. The hardbodied, badass jumped in and broke up the fight.

JJ suffered 2 black eyes, and his suit got shredded, but witnesses tell us he fought the good fight, considering the numbers. JJ believes the attackers were a gang, according to our sources.

We're told he ended up in an ER because he was feeling ill, and friends were worried he had a concussion. For some reason, neither JJ nor anyone on the production chose to call cops about the brawl.

JJ's only consolation -- he doesn't have to get engaged to Kaitlyn. She booted him 4 weeks ago. We hear Clint's still available.