His shares are currently worth $45 billion on paper.
Apparently he and his wife posted the news on his own Facebook page.
Priscilla Chan and Zuckerberg will run the foundation which will foster equality and the potential of people.
Over each of the next three years the couple will sell up to $1 billion shares, but Zuckerberg will still have the controlling share in Facebook.
He has no intention of stepping down as CEO of Facebook.