The Hollywood starlets hit the prom-themed red carpet last night to celebrate the launch of the Kate Young For Target collection decked out in, you guessed it, Kate Young For Target wares. Maggie Gyllenhaal looked bohemian-chic in a one-shoulder printed maxi dress with a pair of suede strappy flats and a rhinestone bracelet; Michelle Williams showed off her new '90s hairdo and cool-girl style in a white blazer, black semisheer top, and navy shorts; and Kate Mara donned a party-ready yellow rhinestone-embellished dress accessorized with a bold cuff and suede peep-toe pumps. We can't think of better (celebrity-styled) examples of why you should nab a piece from the new collaboration once it hits stores and online on April 14. Now, we want to hear from you: which look gets your best-dressed vote?