Facebook's Mark Zuckerberg and his wife Priscilla Chan say they will give away 99% of their shares in the company to good causes as they announce the birth of their daughter Max.
Mr Zuckerberg made the announcement in a letter to Max on his Facebook page.
He said they are donating their fortune to the Chan Zuckerberg Initiative because they want to make the world a better place for Max to grow up in.
The donation amounts to $45bn (£30bn) at Facebook's current value.
However the shares will not be donated to charity immediately, but over the course of the couple's lives.
Max was born last week, although her birth was only made public on Tuesday.
In his letter Mr Zuckerberg said the aim of the Chan Zuckerberg Initiative is "to advance human potential and promote equality for all children in the next generation".
Its initial areas of focus will be personalised learning, curing disease, connecting people and building strong communities.
"Your mother and I don't yet have the words to describe the hope you give us for the future," Mr Zuckerberg said at the start of his letter to Max.
"You've already given us a reason to reflect on the world we hope you live in," it added.