An investment company closely associated with U2 singer Bono stands to make up to $800m (£506m) as a result of Facebook's stock market flotation.
Elevation Partners spent $210m buying Facebook shares in 2009 and 2010, which represents about 1% of the company.
Facebook is now valued at $80bn - $100bn which would give Elevation a huge paper profit when the shares start being publicly traded.
Bono is listed as a managing director and co-founder of Elevation.
The other main investors at the firm include Roger McNamee, who previously founded Silver Lake Partners, one of Silicon Valley's top venture capital firms.
Elevation has had a patchy investment record, including taking a stake in the smartphone company Palm which later saw the iPhone take much of its market.
Facebook announced its flotation plans on Wednesday.
The company said it would seek to raise $5bn, about half the amount many analysts expected.
But the initial public offering (IPO) is still expected to be the biggest sale of shares by an internet company.
Facebook, just eight years old and started by Harvard University students, now has 845 million users and made a profit of $1bn last year.
Facebook filed its intention to float with the Securities and Exchange Commission after the US stock markets closed.