Cristiano Ronaldo Kissing Hot Mystery Chick At Miami Pool

Kiss-tiano Ronaldo????

Seems someone has finally tamed the tan stallion ... because Cristiano Ronaldo was getting VERY up close and personal with a hot blonde in Miami this weekend ... and even planted a kiss on her!

The two were all about the PDA -- holding each other in the pool ... and literally getting on top of each other on the deck chairs.

At one point, a smokin' hot friend came over and began smackin' the lady on her butt -- and no one complained.

Despite all the attention, Ronaldo has yet to put her on his Instagram page -- so, it's not official ... at least not yet.

11:09 AM PT -- MYSTERY SOLVED!!!

The woman is Cassandre Davis -- a Florida-based fitness model who's racked up more than 500k instagram followers due to her ass-centric workout videos.