Facebook founder Mark Zuckerberg and his wife have announced plans to give away 99 percent of their shares in the company - currently worth about $45 billion - to good causes.
The couple revealed plans to donate their fortune to a new charity in a letter, published on Facebook, addressed to their daughter, Max, who was born last week.
Mr Zuckerberg has told the company the first step will see him give away up to $US1 billion worth of his stock for each of the next three years.
The plan mirrors a move by other high-profile billionaires, such as Warren Buffett and Bill and Melinda Gates, who hae set up foundations to give away their fortunes to charity.
On his Facebook page, Mr Zuckerberg posted a photo of himself, his wife, Priscilla Chan and their new daughter, Max, along with a post entitled 'A letter to our daughter.'
In the 2220-word letter, Mr Zuckerberg and Ms Chan touched on issues including health, education, internet access and learning before announcing the Chan Zuckerberg Initiative, which aims to "advance human potential and promote equality."
Mr Zuckerberg, 31, and Ms Chan said they plan to give away 99 percent of their Facebook shares over their lifetimes to advance the initiative, which was formed as a limited liability company controlled by the two. It will begin by focusing on personalised learning, curing disease, internet connectivity and community building.
Max Chan Zuckerberg was born early last week - though Facebook did not specify which day - and weighed 7lbs 8oz ounces at birth. Last month, Mr Zuckerberg announced he would take two months of paternity leave after the birth of his daughter.
Ms Chan and Mr Zuckerberg have so far committed $1.6 billion to their philanthropy. They have given several donations this year, including to public schools, initiatives to bring better wireless internet access and to San Francisco General Hospital, where Ms Chan works as a paediatrician.
When Mr Zuckerberg was 26, he signed the Giving Pledge, under which the world's wealthiest individuals and families commit to give more than half of their wealth to philanthropy or charitable causes over their lifetime or in their will.
Mr Zuckerberg said he still plans to remain CEO of Facebook for "many, many years to come," and Facebook said Mr Zuckerberg is expected to be the controlling stockholder of the company for the foreseeable future.
Mr Zuckerberg and Ms Chan said they will share more details when they return from their parental leave.