Bella Hadid Celebrates 20th Birthday

Bella Hadid just hit the big 2-0 over the weekend, and she did it wearing an outfit that looked like she was honoring the late Joan of Arc.

Paps got Bella out in NYC celebrating her 20th bday with her model friends and fam ... wearing a chain mail 2 piece that rattled around like she was going into battle in the Dark Ages.

Her BF, The Weeknd, was there too ... but Bella's outfit was the clear standout.

Check out the clip -- Bella's bringing armor back.