Her style: Playful, dapper, menswear-inspired

It all started with 1977's "Annie Hall," where Diane Keaton inspired women everywhere with her high-waisted trousers, neckties and bowler hats to transcend traditionally feminine style. Since then, the Oscar-winning actress' fashion influence has earned her icon status.

Over the years, we've seen Keaton in wide leather belts, tweed blazers and shoulder pads -- but her loyalty to structured suits and other menswear-inspired touches has remained constant. What inspires her look? Keaton says she simply wears what she thinks looks good on her, regardless of trends or expectations. Finding what you like and embracing that individuality is key, she says. Hats, gloves, suits, ties, heeled boots, the color black -- these are the elements she has always loved, and her style has simply developed from there.

Photograph courtesy of Ruven Afanador, Random House

Her style: Feminine, simple, high-end

This elegant Venezuelan-born designer "was born into high-end style," explains Style Consultant Sherrie Mathieson. "Her background was very affluent -- well-heeled and well-traveled," and that lay the foundation for her aesthetic.

In her early days, Herrera ran in the same stylish circle as Andy Warhol and former Vogue Editor-in-Chief Diana Vreeland, first landing on the International Best Dressed List in 1972 and in the Best Dressed Hall of Fame in 1980. Today, in her mid-70s, "she manages a natural look, while still being glamorous -- not easy when so many [women her age] look too 'done,'" Mathieson says.

The designer's signature white button-up blouse (collar up, sleeves rolled), paired with a dark taffeta knee-length skirt is a favorite look in the fashion world. Still designing new collections every season, "Herrera's forward-moving lifestyle and two lovely daughters keep her modern and truly ageless," says Mathieson.

Photograph courtesy of Carolina Herrera

Her style: Effortless, elegant, sexy

When the name Diane von Furstenberg comes up, most fashion buffs instantly think one thing: The wrap dress. It was she that invented the famous garment in 1974, which swiftly became a style sensation. And though von Furstenberg still loves the wrap dress ("How can I not?" she told Harper's Bazaar. "It paid ... all my bills."), she is defined by more than a flattering silhouette.

Like Carolina Hererra, Belgian-born von Furstenberg also made many an appearance at Studio 54 in the '70s, when Andy Warhol captured her feline likeness in his pop art portraits. Since then, she has established herself as a symbol of both feminine style and power.

"I like to think that my style ... [is] effortlessly elegant and sexy," she said in an interview with Harper's Bazaar. "I think the word effortless is very important. I think that that creates an ease and a confidence, because I think there's nothing more beautiful than a woman who's confident." Bold prints, flattering silhouettes and a strong sense of self make DVF a household emblem of style.

Photograph courtesy of Vogue

Her style: Glamorous, sumptuous, structured

Discovered by photographer Peter Beard at Nairobi University in Kenya, Somalia-raised fashion model Iman graced the pages of American Vogue in 1976 and soon became the muse for high-end designers from Gianni Versace to Yves Saint-Laurent. In addition to being one of the first-ever black supermodels, Iman is also the founder of the eponymous cosmetics line for women of color.

"When I was modeling, you have to wear whatever they ask you to," Iman told WWD. "When I stopped, I started wearing silhouettes that really work for me." Since then, Iman's style has been defined by luxurious fabrics and structured cuts, such as cashmere sweaters, tailored suits and palazzo pants (her favorite) -- never finished without a piece of statement-making jewelry.

Photograph courtesy of Net-A-Porter

Her style: Edgy, seductive, "porno-chic"

Though smoky-eyed former Vogue Paris Editor-in-Chief Carine Roitfield has been referred to as "the queen of porno-chic," she prefers "erotic-chic" or "rock and roll."

"Porno, you show everything," the fashion writer and stylist told the Observer. "Erotic, you are dreaming about something, about another world.... I try not to show everything." Semantics aside, Roitfield's ever-tousled hair, dark eye makeup and seductive black frocks -- from the sheer to the bodycon -- create an unmistakable aesthetic that proves women over 50 can be very erotic. (Of course, being French doesn't hurt). After all, only "the queen of erotic-chic" would dare to don black lace on the weekend.

Photograph courtesy of AOL Style