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8. Sara Blakely, SPANX

Sara Blakely was dressing for a party in 1998 and needed something to provide a smooth look under white pants. She cut the feet off a pair of control-top pantyhose to create a smoothing, waist-to-toe undergarment, and SPANX was born. After finding a manufacturer, Blakely persisted through rejection after rejection before landing her first big order from Neiman Marcus. When Oprah Winfrey spotlighted the product in her “Favorite Things,” SPANX took off.

Today, SPANX product lines include bras, underwear, leggings, activewear and even men’s compression undershirts. In 2012, Forbes named Blakely the world’s youngest, self-made female billionaire. She has signed the Giving Pledge, committing to give at least half her wealth to charity, and her Spanx by Sara Blakely Foundation has donated millions to charities for women and girls.