At the age of just 44, Sheryl Sandberg has become one of the world’s youngest female billionaires. On Tuesday, the Facebook COO hit the extraordinary financial milestone, with 12.3 million shares and 4.7 million stock options in the successful social media company.

The success of , a book that redefines the notion of ‘having it all’, advocating women support and mentor each other in the workplace but empowering them to feel entitled to success, has also added to her personal fortune.

Sandberg is now part of a very elite female club of just 138 women, all with a 10-figure fortune. That may account for only 10% of the world’s billionaire’s, but still an impressive jump from just 104 women in 2012. The world’s richest woman remains L’Oreal 90-year-old heir Liliane Bettencourt. Former British billionaire J K Rowling is no longer part of the gang as she has given so much of her fortune to charity.

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