Pauly D is ringing in another trip around the sun the only way he knows how -- with a packed Vegas nightclub, booming music and a whole lotta love from the crowd.

The "Jersey Shore" star kicked off his 46th birthday celebration Saturday night at Marquee Las Vegas ... taking over the DJ booth while fans packed the club. At one point, a giant "Happy B-Day Pauly D" sign lit up behind him as the birthday boy soaked in the moment.

Pauly looked right at home behind the decks, hyping up the crowd with his trademark energy, pointing out to fans and grinning from ear to ear as the party rolled on. Safe to say nobody was leaving early.

The birthday bash spilled well into the night ... with clubgoers singing along, dancing shoulder-to-shoulder and giving the reality TV favorite the kind of celebration Vegas does best.

Forty-six never looked so loud ... and if this party's any indication, Pauly D isn't slowing down anytime soon!