They may be young, but the following seven people had the vision and drive to turn themselves into billionaires before they reached the ripe "old" age of forty.
1Yusaku Maezawa: from rock star to mega-rich retailer by age 35
Yusaku Maezawa is a former rock musician who started selling CDs and band t-shirts online back in the early 1990's. He then started a company called Start Today, along with a wildly-successful e-commerce site called Zozotown. Zozotown is set up like a mall, with different shops for different types of fashion and other products that are all sold on consignment.
The company has doubled its value every year since it was established in 2005, and Zozotown currently has over 3 million subscribers (one must subscribe in order to access Zozotown). At age 35, Maezawa is a billionaire and his company is still flourishing despite hard economic times felt elsewhere in the world.
2Mark Zuckerberg: the 26 year-old geek who created an empire
Twenty-six year-old Mark Zuckerberg is the computer savvy Harvard student who created a little website you might have heard of called Facebook. Though there is some controversy over who came up with the idea for the social networking site (see the 2010 blockbuster "The Social Network"), there is no denying that it was Zuckerberg's hard work and brain power that brought Facebook to life and made it the most popular social networking site online today.
To date, Zuckerberg has made over 13.8 billion U.S. dollars. To his credit, Zuckerberg has already donated hundreds of thousands of dollars to charities and recently pledged to donate over half of his fortune to charity either over the course of his lifetime or after his death.
3Yoshikazu Tanaka: the 34 year-old who wants to rule the (social media) world
Watch out, Zuckerberg... Yoshikazu Tanaka is coming for you! Founder of Japan's largest social networking site, Gree, Tanaka (age 34) is already worth over $2.2 billion. Tanaka aims for global expansion and will soon establish a California office for Gree.
The name "Gree" is a play on the expression, "Six degrees of separation."
4Dustin Moskovitz: the 26 year-old who had the best college roommate ever
Just 8 days younger than his Facebook co-founder, Mark Zuckerberg, Dustin Moskovitz was Zuckerberg's Harvard roommate and Facebook's third employee. Serving as Facebook's first Chief Technology Officer and Vice President of Engineering, Moskovitz amassed a self-worth of over $2.7 billion. He left Facebook in 2008 to start his own company, Asana.
5Oleg Bakhmatyuk: an egg-cellent 35 year-old business man
This 35-year-old from western Ukraine is the majority owner of Avangard, Ukraine's largest producer and exporter of chicken eggs.
Yes, chicken eggs! Bakhmatyuk worked previously in the lucrative state gas and oil industry, but moved into egg and egg products because he thinks that businesses will be increasingly interested in feeding the world's hungry people in the future.
6Sergey Brin: you might not know this 38 year-old's name, but you probably used his website today
This thirty-eight year-old Russian-American computer scientist and industrialist co-founded Google, the world's largest Internet company, with Larry Page. As of 2011, his personal wealth is estimated to be $19.8 billion.
7Xiaofeng Peng: the 36 year-old who makes money from the sun.
Xiaofeng Peng, age 36, is Chairman of the Board of Directors and Chief Executive Officer of LDK Solar Co., Ltd. He founded the company in July 2005 and it went public in 2007; it is now worth over $1.8 billion. Peng has made his own personal fortune of $1.5 billion all through renewable solar energy.