FORTUNE — Mark Zuckerberg donated Facebook shares worth $500 million to the Silicon Valley Community Foundation, a non-profit organization that works with donors to allocate funds according to their interests. The gift is the largest ever received by the foundation, which finances projects locally and around the world, and Zuckerberg said he planned to focus his giving in health and education.

Zuckerberg announced the gift in a post on Facebook, where he noted that he and his wife Priscilla Chan had previously signed the Giving Pledge, an effort led by Warren Buffett and Bill Gates to encourage billionaires to donate most of their wealth to philanthropic causes. In 2010, Zuckerberg pledged to donate $100 million in Facebook (FB) shares to an effort to improve public education in Newark, New Jersey.

“Today, in order to lay the foundation for new projects, we’ve made a contribution of 18 million Facebook shares to the Silicon Valley Community Foundation,” Zuckerberg wrote. At Tuesday’s closing price of $27.71, the shares are worth $498 million. “Together, we will look for areas in education and health to focus on next. I’m hopeful we’ll be able to have as positive an impact in our next set of projects,” Zuckerberg wrote.

In a statement, Emmett Carson, CEO of the Silicon Valley Community Foundation said: “Mark’s generous gift will change lives and inspire others in Silicon Valley and around the globe to give back and make the world a better place. We are pleased and honored that he has chosen to continue to partner with us to help him achieve his philanthropic goals.”