The actor/musician went out for a night on the town in Nashville with beautiful gal pal Adria Arjona -- and the couple couldn't keep their hands or lips off each other.

We're told Jason first took care of some biz Monday night ... playing with his band ÖOF TATATÁ to a crowd at Cannery Hall.

After the gig, Jason, Adria and the band members decided to go and hang out at Robert's Western World nearby.

Our sources say Jason and Adria were having a grand ol' time, chatting and dancing as songs were blaring inside the bar. They also grabbed some grub and had a few drinks.

But that was just the appetizer ... Jason's main course was planting a big kiss on the lips of Adria. Check out the vid!

After about an hour, the two decided to call it a night and were photographed walking hand in hand to an SUV outside the saloon. We're told they climbed inside the vehicle and drove away.

Meanwhile, in January, Jason finalized his divorce from Lisa Bonet after 7 years of marriage, beginning in 2017. Yet, the pair separated in 2022, while mutually caring for their two children.

Jason posted Instagram photos this week of himself embracing Adria as they smile together, seemingly confirming their new relationship.