(InStyle.com) -- In show-stopping gowns and barely-there minidresses, these Hollywood icons know how to create major fashion moments. Who can forget Gwyneth Paltrow's cut-out Stella McCartney minidress, or Julia Roberts's legendary vintage Valentino? InStyle fashion director Hal Rubenstein reveals 20 of his favorites.
1. Gwyneth Paltrow, 2008
"Paltrow gives the illusion of giving something away, while still having a kind of ladylike reserve. This sexy mini, by pal Stella McCartney, plays up her best assets and shows off her killer body."
2. Julia Roberts, 2001
"Instead of using a stylist to pick a gown for her Oscar-winning night, Roberts turned to her niece, Emma. This Valentino number gave a huge boost to vintage."
3. Kate Moss, 2005
"On the one hand this Dior couture dress is lingerie-inspired and sexy, yet the shape is quite simple. Finishing off the look with tousled bed-head proves that Moss's instincts are always right."
4. Jennifer Aniston, 2009
"I love the idea of androgyny, and if you're going to do menswear, you have to sex it up. Aniston really played against type in this Burberry Prorsum pantsuit."
5. Beyonce, 2009
"This Elie Saab dress is perfect for her -- it celebrates everything and hides nothing. She understands what works for her body."
6. Marion Cotillard, 2010
"I love the Dior gown, because it plays against opposites-short in front and long in back, glamorous up top and lingerie-inspired on the bottom. Cotillard takes risks that pay off."
7. Penelope Cruz, 2007
"The beautiful pink color of this Atelier Versace gown perfectly accents Cruz's skin, while the silhouette manages to be both sleek and romantic at the same time."
8. Natalie Portman, 2008
"Portman doesn't look like most young stars--she likes to play with volume and proportion. Here, she takes a wild Haute Couture look by Riccardo Tisci for Givenchy and pairs it with perfectly polished hair and makeup."
9. Nicole Kidman, 2003
"Kidman has a fearless approach to fashion. The lavender color of this YSL gown offsets her red hair, while the silhouette is a nice play on proportion."
10. Anne Hathaway, 2009
"This Armani Prive dress has huge wow factor. What's cool is that the iridescent paillettes lengthen her body and accent her curves. It's one thing to have a good body, another to be proud of it!"
11. Cate Blanchett, 2005
"When Valentino approached her to wear one of his dresses to the Oscars the year she was nominated for The Aviator, Blanchett said yes, as long as she was the only one to wear Valentino. She doesn't dress like anyone else."
12. Jessica Alba, 2008
"Six months pregnant at the time, Alba looks radiant in this Marchesa stunner. The jewel tone allows her to positively glow."
13. Leighton Meester, 2009
"Meester is anything but conventional. She is having a blast with fashion, and this Bottega Veneta dress is no exception. The fluidity of this goddess gown is pure glamour. "
14. Eva Mendes, 2009
"In the midst of an economic crisis, this fearless Dior dress brought everyone's spirits up. Mendes knows how to dress for her body and simply has fun with fashion."
15. Rachel McAdams, 2009
"There's something very old Hollywood glamour about her look. This Emanuel Ungaro mini brings her back to that romantic place, while still looking modern."
16. Megan Fox, 2009
"After Fox wore this barely-there number to a premiere, every last red Cavalli dress sold out in three days. Everyone was talking about the way she looked."
17. Keira Knightley, 2006
"The rich burgundy color of this Vera Wang gown is unbelievable. Knightley has a great sense for color, and always chooses tones that get her noticed. She dresses with a French sensibility even though she's British."
18. Jennifer Connolly, 2007
"The metallic shine of this Balenciaga dress works well with her pale skin tone. The short silhouette and hair worn down keep the look young and modern."
19. Carey Mulligan, 2010
"Mulligan doesn't run to the safety of a solid for the red carpet. The print of this Vionnet gown is romantic, while the shape is modern. She's got a level of awareness and quirkiness that sets her apart from other actresses."
20. Kate Beckinsale, 2009
"The bias cut of this J. Mendel gown shows off Beckinsale's curves. She always incorporates one element to make the look a standout, and far from minimal."
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