Kristin Cavallari Birthday Hot Shots ... 39 And So Frigin' Fine!

Let's be honest, Kristin Cavallari has been on the scene for a minute now, but this hot mama is aging like a fine wine -- so, to celebrate her 39th birthday, sip up her hot shots and score with some KC trivia!

Stringy bikinis and seductive poses for days, she's droppin' jaws in so many ways!

What happens in Cabo doesn't always stay in Cabo ... lean back into poolside selfies like this one, which perfectly captures her sexy silhouette!

When she's not a doting mother to her 3 kiddos, catch her outside posing pretty and blocking out the haters 😎!

Check out the gallery and send Kristin your best bday wishes!

For the time being, Kristin's retired her game-playing skills on reality TV, but we got a spicy game for you, can you score the answer?!