Facebook CEO Mark Zuckerberg has said he is donating nearly $500m (€377m) in stock to a Silicon Valley charity with the aim of funding health and education issues.
Mr Zuckerberg donated 18 million Facebook shares, valued at $498.8m based on their Tuesday closing price.
The beneficiary is the Silicon Valley Community Foundation, a non-profit that works with donors to allocate their gifts.
This is Mr Zuckerberg's largest donation to date.
He pledged $100m in Facebook stock to Newark, New Jersey, public schools in 2010, before his company went public earlier this year.
Later in 2010, he joined Giving Pledge, an effort led by Microsoft founder Bill Gates and Warren Buffett to get the country's richest people to donate most of their wealth.
His wife, Priscilla Chan, joined with him.
In a Facebook post, Mr Zuckerberg, 28, said he is "proud of the work" done by the foundation that his Newark donation launched, called Startup: Education, which has helped open charter schools, high schools and others.
With the latest contribution, he added: "We will look for areas in education and health to focus on next."
He did not give further details on what plans there may be for funds.
"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," said Emmett D Carson, CEO of the foundation.