Even though Sheryl Sandberg has not made her letter public, Facebook (NASDAQ:FB) COO has pledged to give away at least half of her $1 billion fortune, as reported by Forbes this week-end. At 44, Sheryl Sandberg is well-known for her “Lean In Foundation”, an non for profit organization advocating for girls and women empowerment.

Facebook Chief Operating Officer Sheryl Sandberg has joined the Giving Pledge, with 127 other billionnaires pledging to give away most of their assets to charity. The Giving Pledge was initiated by Warren Buffet and Bill Gates, who committed to give more than 95% of their fortune.

‘We are thrilled to welcome this diverse group of business leaders and philanthropists to the pledge’ Warren Buffett stated about Sheryl Sandberg and her fellow new Pledgers.

With her $1 billion fortune, Sheryl Sandberg becomes the 2nd self-made bilionnaire to join the Giving Pledge, after Spanx found CEO Sara Blakely.

In 2013, Facebook (NASDAQ:FB) Founder and CEO Mark Zuckerberg had been reported by the Associated Press to be the most generous American philanthropist of the year, with a $970 million donation (consisting of 18 million Facebook (FB) shares).