Mark Zuckerberg named the world's youngest billionaire

Facebook founder Mark Zuckerberg has been named the world's youngest billionaire.

Zuckerberg, 23, started the hit social networking site while at Harvard University and is now worth a staggering $1.5b, according to Forbes.

The tech wizard's fortune is good enough to rank him at 785th spot on Forbes magazine's annual list of the world's richest billionaires.

"He is the youngest self-made billionaire in human history," the magazine's editor-in-chief Steve Forbes said.

The new list also revealed that Bill Gates 13-year reign as the world's richest man is over. The Microsoft founder has been beaten to the top spot by investment mogul Warren Buffett, according to Forbes magazine.

Buffett, the 77-year-old veteran chairman of Berkshire Hathaway, reportedly increased his wealth by $10b to $62b in the last year.

Buffett's increase in wealth came through gains in the shares held by his investment company.

Gates' fortune rose by $2b to an estimated $58b, dropping him to third spot in the prestigious list.

In second place was Mexican telecommunications mogul Carlos Slim, who has an estimated wealth of $60b.

Forbes says that the composition of the world's top 20 billionaires has also shifted.

In 2006 half of the top 20 came from the U.S, but in 2007 that figure had dropped to just four.

Russia has also overtaken Germany as the country with the second-richest country in terms of billionaires.