Ah, to be young and rich. The average age of the world's 946 billionaires is 62, close to retirement, but a handful get to enjoy the trappings of wealth well before crow's-feet set in.
Thirty-three of this year's billionaires--a mere 3%--are under the age of 40. Their combined net worth is $118 billion, giving them an average net worth of $3.6 billion, on par with their grayer counterparts.
The youngest billionaire in the world is German prince Albert von Thurn und Taxis. The 23-year-old monarch first appeared briefly on the list at age 8, the year his father died, making him the youngest billionaire ever on our list.
He didn't appear again until age 18 when he officially inherited his fortune. (Interesting coincidence: His mother Gloria asked her friend, Swatch's Nicolas Hayek, who is now also a billionaire, to manage her son's fortune.)
These days the eligible bachelor lives in the family castle with his mother and sisters, but he is often away racing cars with the Italian auto-racing league.
Von Thurn und Taxis is one of only three billionaires under 30. The other two are the Hariri brothers, Fahd and Ayman, 26 and 28, respectively, who inherited their fortunes from their late father Rafik Hariri, the former Lebanese prime minister who was killed in a car bombing in 2005.
Their older brother Saad, 36, is the clan's head. He is also the one most likely to follow in his father's political footsteps. As Lebanese parliamentary majority leader, Hariri is working on brokering a peace deal in Beirut.
Fahd Hariri and Prince Albert are also two of only four billionaire bachelors under 40.
The others are Google co-founder Larry Page, 34, and Daniel Ziff, 35, whose father made a fortune in publishing and who now runs an investment company with his two brothers.
Page and Ziff are two of just five Americans among the youngsters. Two other young billionaires, including Australia's James Packer and South Korea's Chung Yong-Jin, are divorced.
Slightly more than half made their money from scratch. The world's youngest self-made billionaire is Ukrainian Kostyantin Zhevago, who controls a bank there and is also a deputy in its parliament.
He is five months younger than Sergey Brin, the Google co-founder who recently married Anne Wojcicki in a Caribbean ceremony to which they wore bathing suits. He and his pal Larry Page are the richest of the under-40 club, worth $16.6 billion apiece at the time of our billionaire rankings.
Among the younger crowd, the only female on our list is Hong Kong's 37-year-old Chu Lam Yiu, who founded a flavorings and fragrance business a decade ago and still chairs the company, called Huabao International Holdings.
Next year, she will likely be joined by Yang Huiyan, 25, who was catapulted into the 10-figure club when Country Garden Holdings, a real estate developer run by her father, debuted on the Hong Kong Stock Exchange in April. At the time, she was worth nearly $9 billion, making her China's richest citizen.
Some of these under-40 tycoons have earned a reputation for being frugal--Yahoo! founder Jerry Yang is said to wear sneakers to work and still flies coach. Others clearly don't want too long to spend their riches.
Take coal magnate Andrei Melnichenko, who has made headlines for much more than his energy and banking deals. The 35-year-old Russian reportedly spent $2 million to hire J-Lo to sing at his wife's birthday party in April and is said to have had Christina Aguilera and Whitney Houston serenading the couple at their 2005 wedding.
Still, whether savers or spenders, these individuals probably won't have to wait until age 65 to retire. Lucky for them.