Net worth: $77.2 billion

Age: 86

Country: US

Industry: Diversified investments

Source of wealth: Self-made; Berkshire Hathaway

Berkshire Hathaway CEO Warren Buffett started his prodigious investing career at a young age. As a child he delivered newspapers on his bike, and by 11 the precocious Nebraska native had purchased his first shares in the stock market — Cities Service Preferred at $38 apiece — and sold them for a $5 profit. He was rejected from Harvard Business School, so Buffett went to Columbia Business School instead and learned under iconic value investor Benjamin Graham, who would become a mentor to the budding financier. Buffett worked as a securities analyst in the early-1950s before starting his own investment firm. He bought textile company Berkshire Hathaway in 1969, transforming it into a holding company that would house the many lucrative investments that helped build his massive fortune and earn the nickname "The Oracle of Omaha."

The array of portfolio companies and investments that made him rich may appear random — he's bet on companies including Coca-Cola, American Express, Geico, Fruit of the Loom, Dairy Queen, and General Motors — but they're all cash-generating machines that offer long-term value. In the past year, his net worth has increased by $13.1 billion.

A frugal man with a fondness for junk food, perhaps the most impressive part of Buffett's $60 billion fortune is that it doesn't include the more than $25 billion he's already given away. He's good friends with Microsoft cofounder Bill Gates, whom he collaborated with to create the Giving Pledge, a promise for billionaires to give away at least half of their wealth to charity.