Stars in Fall Fashion

Dressed in a tailored tuxedo jacket by Rag & Bone, Kate Bosworth pulled off one of fall's biggest looks-menswear. Her buttoned-up shirt and black boots completed the masculine look.

Jessica Biel is ready for fall in a Chanel dress and jacket. Opaque tights and peep-toe pumps finished off her monochromatic look. She also accessorized with several beaded necklaces.

Wide-leg trousers are fall's antidote to the skinny jeans, and when worn with heels, can makes legs look long and lean. Drew Barrymore matched hers with platform shoes, a skinny scarf, gold hoops and bangles.

This midriff-baring mama covered up on a cool day in Paris, with a belted jacket and dark skinny jeans. On her feet, Gwen Stefani wore a year-round classic-black ballet flats.

Pairing an autmnal orange-and-brown shirt with black wide-leg pants, Jennifer Lopez looked casual but chic as summer came to an end. The singer also wore two of her favorite accessories-a bohohemian wide-brimmed hat and an oversize bag.

With legs that go for miles, Liv Tyler is the perfect candidate for another of fall's looks-sweater dresses. The actress paired her cozy knit mini-dress with tall boots.

Ready for wet weather, Ashley Olsen tucked her jeans into a pair of Hunter wellies and stayed covered up in a black coat with elbow patches. Her pumpkin-orange bag is a surefire accessory for fall.

A classic trench never goes out of style. Kate Hudson wore her stone, knee-length coat with jeans tucked into a pair of casual flat boots-another must-have item for fall.

Hilary Duff layered on the accessories at a Chanel event in Beverly Hills. The actress-singer wore tights with her short-sleeve Chanel mini-dress, and topped it off with a beret, a bracelet and multiple necklaces.

Perfectly color coordinated in olive green, Penelope Cruz chose an enturing staple-a woolen turtleneck sweater. Her tall leather boots and a brown leather hobo finished the city-chic outfit.

This British supermodel is known for setting trends-so it's a sure thing that gray is hot this fall. Kate Moss's light gray sweater and tailored blazer matched her skinny jeans, as did her silver flats.

As the weather cools, celebrities are starting to cover up on the red carpet. At Fashion Rocks, Mary J. Blige wore a sophisticated statement coat-dress with a black beret and patent leather shoes.

Amanda Peet strikes a pose in an outfit that's perfect for work or a night out on the town-a dress and trench coat, heels and opaque black tights.

This Oscar-winning actress manages to look casual and sexy in her fitted T-shirt and jeans, which were pulled together with a low-slung metallic belt and seductive stilettos.

Katharine McPhee layered a long-sleeve T-shirt under her taupe jumper, then pumped it up with a bold purple oversize clutch. A perfect trick for extending warm-weather dresses into fall.

It's time to break out the leather jackets. Katie Holmes dons a short brown version with multiple zippers for a cool and contemporary look.

Rachel Bilson favors a casual yet classic look that's ideal for fall-boot-cut jeans, a long-sleeve T-shirt, well-worn boots and a printed silk scarf.

Feeling the cold? Throw a knit wrap over almost anything in your closet, just like Jessica Simpson. The singer also wore dark denim and carried a snakeskin bag.

A fitted jacket is a great way to accentuate an hourglass figure. Anne Hathaway wore one, and picked up on another big trend for fall-black and gold-with her handbag.

In London, Keira Knightley went for a more androgenous look in an oversize shirt, leggings and casual leather harness boots. Her canvas shopping bag came from a local cheese shop.

Known for her unconventional style, Chloe Sevigny made no exception with this outfit. The actress paired a silky mini-dress with lace-up oxford boots and a leather biker jacket for a downtown fall look.

Scarves are a great way to keep warm as the temperature drops. Ashlee Simpson paired her gray (that color again!) one with a cable-knit cardigan and tall boots while in New York.

A transitional coat will see you through fall and into winter, and looks good with almost anything. Jamie-Lynn Sigler's navy-blue military coat is a great example.

An easy fall look can be put together by throwing a short jacket over a camisole and jeans. Claire Danes wore a gray Stella McCartney jacket over a Zac Posen top and Diesel jeans.

Big sunglasses are still in vogue this season. Jessica Alba wore a pair, and added a colorful scarf to her jeans, T-shirt and sneakers for a casual weekend look.

Also on InStyle.com: Exclusive discounts on must-have fall items at your favorite stores!