Andreessen invented Mosaic, the browser that popularized the web, when he was still at UIUC in 1992. He graduated from UIUC's computer science program in 1993 and was only 22 years old when he was recruited by the legendary entrepreneur Jim Clark to start Netscape Communications. Together, they created Netscape Navigator, one of the first and most widely used commercial web browsers ever.

Andreessen also cofounded Opsware (formerly Loudcloud) and sold it to HP for $1.6 billion in 2007. He now runs Andreessen Horowitz, one of the most prominent venture capital firms in Silicon Valley.

Ellison, who founded Oracle, grew up outside of Chicago and attended UIUC for two years. Although he dropped out after his sophomore year because his adoptive mother had died, Ellison showed signs of brilliance at an early age, even being named the science student of the year at UIUC.

Since its founding in 1977, Oracle went on to become one of the largest enterprise tech companies in the world. Last year, it had over $38 billion in revenue, with more than 122,000 employees worldwide. Ellison is the third-richest man on the Forbes List with a net worth of $52.5 billion.

Levchin, a computer science grad in 1997, is one of the cofounders of the online money transfer service PayPal. The cofounders of PayPal, widely known as "PayPal Mafia," also include Peter Thiel and Elon Musk. 

Levchin pitched his idea for what had become PayPal to Thiel over breakfast after meeting for the first time at a Stanford lecture. Thiel wrote the first check for PayPal, and Levchin was named the company’s CTO. Eventually, eBay bought PayPal for $1.5 billion in 2002.

Chen and Karim, both from UIUC’s College of Engineering, cofounded the video-sharing website YouTube in 2005. 

A year later, it was acquired by Google for $1.65 billion. Time Magazine also named it the Invention of the Year in 2006.

Chen and Karim were also early employees of PayPal.

Most people associate Tesla with its current CEO, Elon Musk, but it was Eberhard (computer engineering grad) who first incorporated the company in 2003 with Marc Tarpenning. Eberhard served as CEO until 2007, while Musk was its largest investor and chairman. 

It's unclear what exactly prompted Eberhard to lose his CEO position, but reports indicate he was ousted after Musk lost confidence in him. It led to a lawsuit in which Eberhard sued Musk, accusing him of libel, slander, and breach of contract.

Eberhard told Autoblog in 2010 that he was working with Volkswagen on an electric vehicle project.

Stoppelman founded Yelp, the online reviewing site, in 2004, after graduating from UIUC's computer engineering program in 1999. He spent some time at PayPal while attending Harvard Business School but dropped out to start Yelp.

Stoppelman was the VP of engineering at PayPal and is often mentioned as one of the "PayPal Mafia" members. At PayPal, he also met Max Levchin, who was one of the early investors of Yelp.

Yelp is now publicly traded and had revenue of roughly $232 million in 2013.

Siebel, the founder of Siebel Systems, earned his bachelor's, master's, and MBA at UIUC. 

Siebel Systems was a leading software company that sold CRM applications, until it was acquired by Oracle for $5.8 billion in 2005.

Siebel is now the CEO and chairman of the smart energy firm C3 Energy. Forbes estimates his net worth to be over $2.3 billion.

Eich, who received his master's degree from UIUC, founded the Mozilla project in 1998. It later spun out the Mozilla Corporation, which was responsible for creating the Mozilla Firefox browser.

Eich was also one of the early members of Netscape Corporation, for which he created a new coding language called JavaScript. 

Eich stepped down as Mozilla's CEO in 2014 after he was criticized for supporting an anti-gay marriage campaign. 

Ozzie was a computer science student at UIUC when he started working on PLATO system, which later evolved into Lotus Notes, one of the earliest enterprise collaboration software tools. Lotus was later sold to IBM for $3.5 billion.

Ozzie then founded another collaboration startup, Groove, which was acquired by Microsoft. He then served as CTO and chief software architect at Microsoft from 2005 to 2010. At age 59 he just launched another startup, a collaborative voice-calling app called Talko.

AMD, the semiconductor company that makes computer processors, was founded in 1969 by Sanders and seven former Fairchild Semiconductor employees. 

Sanders was director of marketing at Fairchild and is known for being one of the best salespeople in the semiconductor industry. He turned AMD into one of the biggest competitors of Intel at one point, and he is widely credited for helping drop chip prices.

Sanders stepped down as CEO in 2002. AMD had $5.3 billion in sales last year.

Check out 17 companies you didn't know were founded by MIT grads!