Selena Gomez & The Weeknd Pack On PDA in Italy

Selena Gomez dating the The Weeknd is even a big deal over in Italy.

The couple popped up Friday in Florence where they took in the local art at the famed Uffizi Gallery Museum. We're told there were about 20 people waiting to get in who were pushed aside so Selena and her beau could get out. There was at least one bodyguard with them.

Seems like things are getting serious, our source says they even kissed in public ... as they were boarding an employee elevator to make their exit.

It's interesting ... Selena's BFF, Taylor Swift, jetted off to Italy with Tom Hiddleston when they first started dating, and we know how that ended.