We got Bhad Bhabie and Yachty Tuesday night heading into Ohm Nightclub in Hollywood where they were celebrating her 16th birthday. But, check out the massive new accessory around her neck ... it's a sick $53k chain courtesy of Yachty.

Check out the vid ... Yachty surprised her at her crib in L.A. with the gift and she was all about it. She also showed us some of her other gifts. You already know about her hot new timepiece.

As you know ... Bregoli's "Gucci Flip Flops" featured Yachty, and was a huge hit for them -- it's been certified gold. The two have been close ever since. On her birthday, Yachty called Bregoli his baby sister on Instagram with a twisted, yet hilarious, shout-out.

Yachty said, "I love u like u was my own blood. Of course ur not black but if u was I'm sure you'd be apart of my family.... although if you were, my mom probably would have beaten the nonsense out of you and u wouldn't be where you are now so successful and all that so maybe it's best we're just siblings by spirit."

Classic.

Once inside the club, Bregoli partied her ass off but SOMEONE seemed to be way too focused on her toes. She also had a pretty bhad ass cake!!!

10:11 AM PT -- Turns out the epic bday piece took 10 days to make. Yachty went to Jewelry Unlimited in ATL and ordered the 14k rose and white gold pendant filled with 45 carats worth of diamonds.

Sweet, sweet 16.