The 36-year-old Kardashian sister showed off her amazing slim figure in the outfit, which had us all asking, how has she had three kids?
Kourtney might have been a third wheel on the red carpet at the birthday bash with mom Kris Jenner and her boyfriend, Corey Gamble, but she fit right in with the supermodels inside the party.
The Keeping Up With the Kardashians star certainly held her own amongst a posse of top models including her sister Kendall Jenner and her leggy friends Cara Delevingne and Gigi Hadid.
“Just us supermodels,” she caption a pic on Instagram.
The A-list party, hosted at billionaire Ron Burkele’s Beverly Hill estate, drew many other famous faces including Jay Z, Heidi Klum, Amber Rose, Scooter Braun, Joe Jonas, Vin Diesel, possibly newly single Tyga and more.
Kendall also shared a silly picture with her big sister, who appears to be letting loose following her drama-filled breakup from Scott Disick in July.