Facebook CEO Mark Zuckerberg has sold around $2.3 billion of his shares in the company, in order to pay a tax bill.
Zuckerberg owns around a third of the company, a share worth more than $40 billion based on its current share price of $55.
Facebook itself will also sell 27 million shares in the company, raising about $1.5 billion in the process for undisclosed purposes.
Facebook's share price has risen by more than 45% since its initial public offering in May 2012 - at which they were first offered at $38 and then fell to nearer $20. But following strong revenue growth and sales projections, confidence in the company has been restored and the price has surged.
Zuckerberg's voting share in the company is higher than his share of ownership. It's currently around 60%, but after selling 41.4 million shares it will be reduced to around 56%.
But don't worry too much about the billionaire mogul - his decision to sell doesn't indicate any money troubles. Zuckerberg is merely selling them to pay tax on another share transaction, in which he exercised the option to buy 60 million Facebook shares.
The site's founder and his wife Priscilla Chan will also donate about $1 billion worth of shares to charity by the end of the year, it was reported. The money will go to the Silicon Valley Community Foundation.
Zuckerberg was the second-biggest donator to charity last year in the US, after Warren Buffett, according to The Chronicle of Philanthropy.