Kendall Jenner -- Check Out My Ass and Side Boob ... You're Welcome, Calvin!

Kendall Jenner gave her wardrobe department the day off ... so she could do an awesome underwear photoshoot.

Baring nearly all -- for her art, of course -- Kendall sported the always-in-style hand bra and a tiny black thong for the new Calvin Klein ad.

Check out the video that also featured other scantily clad models: Joan Smalls, Isabeli Fontana and Edita Vilkeviciute.