Ronnie Ortiz-Magro Kisses Woman in Chicago Nightclub

Ronnie Ortiz-Magro is single and very much ready to mingle ... because he's back on the nightclub scene, making out with women ... and it's all on video.

The 'Jersey Shore' star looked in his element Friday night at Tunnel in River North Chicago, locking lips with a blonde.

Folks who were there say Ronnie hit up the club with a buddy, and the woman he kissed was already in the joint when the reality TV star showed up ... the flirty duo didn't come together.

Ronnie seemed like a big hit in the club, and not just with the ladies ... he also took a bunch of photos with fans.

We're told Ronnie didn't get too rowdy or anything, and he wasn't seen drinking alcohol.

Remember, Ronnie told us last year he's sober ... and he's only a few months removed from calling off his engagement to Saffire Matos.