Kourtney Kardashian
This one is simple: Just grab your BF's sweatshirt, if it's big enough, and throw it on as a makeshift dress. Pair with knee-highs and you're set.
Sienna Miller
If you're a jeans and T-shirt kind of gal, a classic camel coat and old school loafers will give your look a cool-and-collected vibe.
Gabrielle Union
Canadian tuxedo anyone? The boys have been doing denim-on-denim forever, but it looks equally as posh in a skirt and collared shirt combo for the ladies.
Ciara
If you have a dressy occassion on the books, swap your cocktail dress for a fitted tuxedo in black & white. Ditch the shirt and play up the low neckline for a sexy take, too.
Cara Delevinge
Boys have been wearing camo since childhood, but in a cool, oversized jacket (complete with rad patches), it's the perfect addtion to help take your summer wardrobe into fall.
Karlie Kloss
You can never go wrong with black. For a feminine take on a traditional suit, go for a shrunken and fitted version that cuts off at the ankles and wrists.
Kristen Stewart
A blazer instantly adds a cool factor to any outfit. Bonus points if it's tweed and grey, the neutral color goes with everything.
Gigi Hadid
Pinstripes are classic, especially if you're talking about a suit. For a flirty vibe, go bold with the colors and pair it with a trendy crop top.
Diane Kruger
Boyfriend jeans are a classic example of borrowed from the boys fashion done right. For an updated take, try a frayed version, like the celebs.
Rita Ora
Crisp, white collared shirts are the uniform of business men everywhere. Jazz up yours with a cropped sweater over the top for a relaxed feel.
Hailey Baldwin
Varsity jackets were popular with the boys at school, but throwing a personalized, grown-up version over your weekend uniform is all the rage in Hollywood.
Jessica Alba
The gents love their flannels, but so do the girls. As temps start to drop, grab one for yourself and add it as a light layer to any of your fall looks.