Kendall Jenner's a well-known supporter of the "Free the Nipple" movement -- and on Sunday, she proved her advocacy yet again.

The model was seen out Sunday in NYC in a barely there see-through red blouse, which put her assets on full display. 

This definitely isn't her first time unburdening her nips -- she was recently doing just that at a beach party in Mykonos ... and who could forget last year's hang out sesh with her girls?

It's about 80 degrees in the city right now ... looks like she must've caught a draft here.