Shares in Facebook, which have doubled in value this year, fell 0.9 per cent yesterday on the news to close at $55.05 per share.
Zuckerberg will use the proceeds of the sale to pay off taxes associated with his exercising of an option to purchase 60m Class B shares in the company.
Facebook said it intends to use the net proceeds of its 27m share offering – around $1.4bn – for working capital and other general purposes.
Each Class A share is entitled to one shareholder vote, while Class B shares are entitled to ten votes and are convertible at any time into one Class A share.
The sale comes just before Facebook’s entry to the S&P 500 Index, the most widely tracked equity index in the world, at the close of trading tonight.
The sale will also reduce Zuckerberg’s voting power in the social network from 58.8 per cent to 56.1 per cent according to the company’s filings.
Board member Marc Andreessen announced he will also sell 1.65m Class A shares.