1. Russian business tycoon and Chelsea Football Club owner Roman Abramovich was born into poverty and orphaned at age 2.
Net worth: $8.2 billion
Abramovich was born in southern Russia, into poverty. After being orphaned at age 2, he was raised by an uncle and his family in a subarctic region of northern Russia. While a student at the Moscow Auto Transport Institute in 1987, he started a small company producing plastic toys, which helped him eventually found an oil business and make a name for himself within the oil industry. Later, as sole leader of the Sibneft company, he completed a merger that made it the fourth biggest oil company in the world. The company was sold to state-run gas titan Gazprom in 2005 for $13 billion.
He acquired the Chelsea Football Club in 2003 and owns the world's largest yacht, which cost him almost $400 million in 2010.
2. Montpellier rugby club president and Entrepreneur of the Year Mohed Altrad survived on one meal a day when he moved to France.
Net worth: $1 billion
Born into a nomadic tribe in the Syrian desert to a poor mother who was raped by his father and died when he was young, Altrad was raised by his grandmother, who banned him from attending school, in Raqqa, the city that is now capital of ISIS.
Altrad attended school anyway, and when he moved to France to attend university, he knew no French and lived off of one meal a day. Still, he earned a PhD in computer science, worked for some leading French companies, and eventually bought a failing scaffolding company, which he transformed into one of the world's leading manufacturers of scaffolding and cement mixers, Altrad Group.
He has previously been named French Entrepreneur of the Year and World Entrepreneur of the Year.
3. Kenny Troutt, the founder of Excel Communications, paid his way through college by selling life insurance.
Net worth: $1.5 billion
Troutt grew up with a bartender dad and paid for his own tuition at Southern Illinois University by selling life insurance. He made most of his money from phone company Excel Communications, which he founded in 1988 and took public in 1996. Two years later, Troutt merged his company with Teleglobe in a $3.5 billion deal.
He's now retired and invests heavily in racehorses.
4. Starbucks's Howard Schultz grew up in a housing complex for the poor.
Net worth: $2.9 billion
In an interview with British tabloid Mirror, Schultz says: "Growing up I always felt like I was living on the other side of the tracks. I knew the people on the other side had more resources, more money, happier families. And for some reason, I don't know why or how, I wanted to climb over that fence and achieve something beyond what people were saying was possible. I may have a suit and tie on now but I know where I'm from and I know what it's like."
Schultz ended up winning a football scholarship to the University of Northern Michigan and went to work for Xerox after graduation. He then took over a coffee shop called Starbucks, which at the time had only 60 shops. Schultz became the company's CEO in 1987 and grew the coffee chain to more than 16,000 outlets worldwide.
5. Investor Ken Langone's parents worked as a plumber and cafeteria worker.
Net worth: $2.8 billion
To help pay for Langone's school at Bucknell University, he worked odd jobs and his parents mortgaged their home.
In 1968, Langone worked with Ross Perot to take Electronic Data Systems public. (It was later acquired by HP.) Just two years later, he partnered with Bernard Marcus to start Home Depot, which also went public, in 1981.
6. Born into poverty, Oprah Winfrey became the first African-American TV correspondent in Tennessee.
Net worth: $3 billion
Winfrey was born into a poor family in Mississippi, but this didn't stop her from winning a scholarship to Tennessee State University and becoming the first African-American TV correspondent in the state at the age of 19.
In 1983, Winfrey moved to Chicago to work for an AM talk show that would later be called The Oprah Winfrey Show.
7. John Paul DeJoria, the man behind a hair-care empire and Patron Tequila, once lived in a foster home and his car.
Net worth: $2.9 billion
Before the age of 10, DeJoria, a first-generation American, sold Christmas cards and newspapers to help support his family. He was eventually sent to live in a foster home and even spent some time in a gang before joining the military.
With a $700 dollar loan, DeJoria created John Paul Mitchell Systems and sold the shampoo door-to-door while living in his car. He later started Patron Tequila, and now invests in other industries.
8. At one time, businessman Shahid Khan washed dishes for $1.20 an hour.
Net worth: $4.4 billion
He's now one of the richest people in the world, but when Khan came to the U.S. from Pakistan, he worked as a dishwasher while attending the University of Illinois. Khan now owns Flex-n-Gate, one of the largest private companies in the U.S., the NFL's Jacksonville Jaguars, and Premier League soccer club Fulham.
9. Forever 21 founder Do Won Chang worked as a janitor, as a gas station attendant, and in a coffee shop when he first moved to the U.S.
Net worth: $6.5 billion
Husband and wife Do Won Chang and Jin Sook, the team behind Forever 21, didn't always have it so easy. After moving to the U.S. from Korea in 1981, Do Won had to work three jobs at the same time to make ends meet. The couple opened their first clothing store in 1984.
Forever 21 is now an international, 480-store empire that rakes in around $3 billion in sales a year.
10. Ralph Lauren was once a clerk at Brooks Brothers dreaming of men's ties.
Net worth: $6.8 billion
Lauren graduated high school in the Bronx, New York, but later dropped out of college to join the Army. It was while working as a clerk at Brooks Brothers that Lauren questioned whether men were ready for wider and brighter designs in ties. The year he decided to make his dream a reality, 1967, Lauren sold $500,000 worth of ties. He started Polo the next year.
11. Steel tycoon Lakshmi Mittal came from modest beginnings in India.
Net worth: $12.3 billion
A 2009 BBC article says the ArcelorMittal CEO and chairman, who was born in 1950 to a poor family in the Indian state of Rajasthan, "established the foundations of his fortune over two decades by doing much of his business in the steel-industry equivalent of a discount warehouse."
Today Mittal runs the world's largest steel-making company and is a multibillionaire.
12. Luxury goods mogul Francois Pinault quit high school in 1974 after being bullied for being poor.
Net worth: $14.2 billion
Pinault is now the face of fashion conglomerate Kering (formerly PPR), but at one time, he had to quit high school because he was teased so harshly for being poor. As a businessman, Pinault is known for his "predator" tactics, which include buying smaller firms for a fraction of the cost when the market crashes. He eventually started PPR, which owns high-end fashion houses including Gucci, Stella McCartney, Alexander McQueen, and Yves Saint Laurent.
13. Leonardo Del Vecchio grew up in an orphanage and later worked in a factory where he lost part of his finger.
Net worth: $24.1 billion
Del Vecchio, one of five children, was eventually sent to an orphanage because his widowed mother couldn't care for him. He would later work in a factory making molds of auto parts and eyeglass frames.
At the age of 23, Del Vecchio opened his own molding shop, which expanded to become the world's largest maker of sunglasses and prescription eyewear, including the brands Ray-Ban and Oakley.
14. Legendary trader George Soros survived the Nazi occupation of Hungary and arrived in London as an impoverished college student.
Net worth: $24.2 billion
In his early teens, Soros posed as the godson of an employee of the Hungarian Ministry of Agriculture to stay safe during the Nazi occupation of Hungary. In 1947, Soros escaped the country to live with relatives in London. He put himself through the London School of Economics working as a waiter and railway porter.
15. After his father died, business magnate Li Ka-shing had to quit school to help support his family.
Net worth: $27.1 billion
Ka-shing fled mainland China for Hong Kong in the 1940s, but his father died when he was 15, leaving him responsible for supporting his family. In 1950, he started his own company, Cheung Kong Industries, which manufactured plastics at first but would later expand into real estate.
16. College dropout Sheldon Adelson grew up sleeping on the floor of a Boston tenement house.
Net worth: $29.5 billion
Adelson, the son of a cab driver, grew up in Dorchester, Massachusetts, and began selling newspapers at the age of 12, reports Bloomberg Businessweek.
A Forbes profile of the billionaire says that years later, after dropping out of the City College of New York, Adelson "built a fortune running vending machines, selling newspaper ads, helping small businesses go public, developing condos, and hosting trade shows."
Adelson lost almost all of his money in the great recession, but he has earned much of it back. He now runs Las Vegas Sands, the largest casino company in the world, and is considered the most high-profile political donor in America, says Forbes.
17. Oracle co-founder Larry Ellison dropped out of college after his adoptive mother died, and he held odd jobs for eight years.
Net worth: $49.8 billion
Born in Brooklyn, New York, to a single mother, Ellison was raised by his aunt and uncle in Chicago. After his aunt died, Ellison dropped out of college and moved to California to work odd jobs for the next eight years. He founded software development company Oracle in 1977, which is now one of the largest technology companies in the world.