Kourtney Kardashian is 38 and feeling great!

The reality star rang in her birthday on Instagram on Tuesday, with a super sexy (and slightly NSFW) pic of herself hair-flipping in a swimming pool.

"Birthday suit," Kourtney captioned the snap, nodding to her naked figure.

WATCH: Kourtney Kardashian Receives Fun Birthday Wishes From Her Family as She Turns 38

It's been a good birthday for the mother of three, who also received birthday wishes from her family and loved ones.

Happy birthday, Kourtney!

WATCH: Scott Disick Admits Kourtney Kardashian Still Turns Him On, Says He'll 'Never Be Over Her'

Meanwhile, Kourtney and her ex, Scott Disick, were recently spotted out together again in Hawaii.

Watch the video below for the paradise pic.