Black or blue, skinny, or borrowed-from-your-boyfriend, denim is a wardrobe essential. Even celebs, who are usually getting glammed up in glitzy red carpet-ready dresses, wear jeans on their days off. Dressed up and dressed down, here's a round-up of Allison Williams, January Jones, Zoe Saldana, Miranda Kerr, and more of your favorite street stylistas in enviable—and wearable—denim looks you'll be dying to try. The best thing about these outfits? We know you've already got the most important part in your closet.