Happy birthday to YOU, Kylie Jenner!

The young mom is celebrating her 22nd birthday with a floating party in the Tyrrhenian Sea off the island of Capri in Italy with "hubby" Travis Scott, mom Kris Jenner and boyfriend Corey Gabmle, new BFF Sofia Richie and her man Scott Disick, and a few other pals. But it's her daughter Stormi who brought Ky her greatest joy today, singing Happy Birthday Day to her mom ... and the little lady can actually carry a tune! Sounds like she gets it from her daddy, moreso that her mom :)

So onto the gifts -- somebody organized a huge sunflower sculpture spelling out "22" on the deck of the luxury yacht Tranquility that Ky booked for a cool $1.2 MILLION for the week. But it was the drip from Travis that stole the show -- a diamond-encrusted chain with a Kylie Lip Kit logo charm front and center, literally dripping in more diamonds. No wonder it's called drip!