See which celebs have donned the Project Runway judge's designs on the red carpet
The Zero Dark Thirty actress has Posen to thank for providing one of her favorite red carpet memories. "The Zac Posen dress on the red carpet at Cannes [is my favorite look I've worn]! I wanted to wear a dress that looked like sunshine," Chastain tells Us. "Holding hands with Sean Penn and Brad Pitt while wearing that yellow dress is a moment I'll never forget."