Bella Hadid was brought to her knees ... in the most unflattering way possible.

Bella was leaving Cipriani Wednesday night in NYC ... doing what super models do -- strutting her goods down some stairs in knee-high boots as paps snapped and flashed away.

All seemed fine ... until Bella slipped on the last step and ate it. Pretty clear she was embarrassed by the whole thing -- turning her back and covering her face. Even more embarrassing? Her boots say "FOR WALKING" on them.

But don't shed any tears for her ... she got to party with her fave baddies -- Kendall Jenner and Hailey Baldwin.