Kendall Jenner knows how to turn up the heat ... and she did just that in a new photo spread as she cooled off poolside -- in her topless bikini!

The model recently posted a series of pics on Instagram showing her sunbathing next to the pool with her back to the photog and wearing just her thong bikini bottom.

In one photo, Kendall is all wet after rising up from the pool and adjusting her bikini. In others, she stares into the camera with sultry eyes, while posing on a lounge chair or at the edge of the pool.

Check out all the snapshots for yourself ... you won't be disappointed. And no caption needed here, BTW ... and Kendall didn't bother writing one.

Several of Kendall's celebrity friends gave their stamp of approval by liking her sexy post, including Hailey Bieber, Gigi Hadid, Lauren Sanchez and Candice Swanepoel.

This is all about her incredible bod!