"PayPal Mafia" is a term used to indicate a group of former PayPal employees and founders who have since founded and developed additional technology companies such as Tesla Motors, LinkedIn, Matterport, Palantir Technologies, SpaceX, YouTube, Yelp, and Yammer. Most of the members attended Stanford University or University of Illinois at Urbana–Champaign at some point in their studies. Several also attended the Illinois Mathematics and Science Academy during high school. Three members, Peter Thiel, Elon Musk, and Reid Hoffman, have become billionaires.
Originally, PayPal was a money-transfer service offered by a company called Confinity which was acquired by X.com in 1999. Later X.com was renamed PayPal and purchased by eBay in 2002. The original PayPal employees had difficulty adjusting to eBay's more traditional corporate culture and within four years all but 12 of the first 50 employees had left. They remained connected as social and business acquaintances, and a number of them worked together to form new companies in subsequent years. This group of PayPal alumni became so prolific that the term PayPal Mafia was coined. The term gained even wider exposure when a 2007 article in Fortune Magazine used the phrase in its headline and featured a photo of former PayPal employees in gangster attire.
The PayPal Mafia are sometimes credited with inspiring the re-emergence of consumer-focused Internet companies after the dot com bust of 2001. The PayPal Mafia phenomenon has been compared to the founding of Intel in the late 1960s by engineers who had earlier founded Fairchild Semiconductor after leaving Shockley Semiconductor. They are discussed in journalist Sarah Lacy's book Once You're Lucky, Twice You're Good. According to Lacy, the selection process and technical learning at PayPal played a role, but the main factor behind their future success was the confidence they gained there. Their success has been attributed to their youth; the physical, cultural, and economic infrastructure of Silicon Valley; and the diversity of their skill-sets. PayPal's founders encouraged tight social bonds among its employees, and many of them continued to trust and support one another after leaving PayPal. An intensely competitive environment and a shared struggle to keep the company solvent despite many setbacks also contributed to a strong and lasting camaraderie amongst former employees.
Individuals whom the media refers to as members of the PayPal Mafia include:
- Peter Thiel, PayPal founder and former chief executive officer who is sometimes referred to as the "don" of the PayPal Mafia
- Max Levchin, Founder and chief technology officer at PayPal sometimes called the "consigliere" of the PayPal Mafia
- Elon Musk, is founder of X.com which acquired the company Confinity. Musk later co-founded Tesla Motors and SpaceX, and is the Chairman of SolarCity
- David O. Sacks, former PayPal COO who later founded Geni.com and Yammer
- Scott Banister, former Ironport CTO and PayPal board member
- Roelof Botha former PayPal CFO who later became a partner of venture capital firm Sequoia Capital
- Steve Chen, former PayPal engineer who co-founded YouTube.
- David Gausebeck, former PayPal Technical Architect, co-creator of the Gausebeck-Levchin test, co-founder of Matterport Inc., a digital 3-D modeling company. 
- Reid Hoffman, former executive vice president who later founded LinkedIn and was an early investor in Facebook, Aviary, Friendster, Six Apart, Zynga, IronPort, Flickr, Digg, Grockit, Ping.fm, Nanosolar, Care.com, Knewton, Kongregate, Last.fm, Ning, and Technorati
- Ken Howery, former PayPal CFO who became a partner at The Founders Fund
- Chad Hurley, former PayPal web designer who co-founded YouTube
- Eric M. Jackson, who wrote the book The PayPal Wars and became chief executive officer of WND Books and co-founded CapLinked.
- Jawed Karim, former PayPal engineer who co-founded YouTube.
- Rod D. Martin, former special counsel to CEO Peter Thiel whose 10X Capital took over Galectin Therapeutics in 2009 and who founded Advanced Search Laboratories in 2012.
- Dave McClure, a former PayPal marketing director, a super angel investor for start up companies and founder of 500 Startups which has hit 500+ investments. 
- Andrew McCormack, co-founder of Valar Ventures 
- Luke Nosek, PayPal co-founder and former vice president of marketing and strategy, became a partner at The Founders Fund with Peter Thiel and Ken Howery
- Jason Portnoy, former vice president of financial planning and analysis who later became CFO at Peter Thiel's Clarium Capital, CFO at Palantir Technologies, and founding partner at Subtraction Capital.
- Keith Rabois, a former executive at PayPal who later worked at LinkedIn, Slide, Square, and currently Khosla Ventures, and personally invested in Tokbox, Xoom, Slide, LinkedIn, Geni, Room 9 Entertainment, YouTube, and Yelp.
- Jack Selby, former vice president of corporate and international development at PayPal who co-founded Clarium Capital with Peter Thiel, later becoming managing director of Grandmaster Capital Management.
- Premal Shah, former product manager at PayPal, became the founding president of Kiva.org.
- Russel Simmons, former PayPal engineer who co-founded Yelp Inc.
- Jeremy Stoppelman, former vice president of technology at PayPal who later co-founded Yelp, Inc.
- David Wallace, a former head of customer service at PayPal who later founded Veritas Christian Academy.
- Yishan Wong, a former engineering manager at PayPal, later worked at Facebook and became the CEO of Reddit.
- Staff Writer. "David Sacks: Biography". Wall Street Journal online. Retrieved August 30, 2013.
- Duke Harris (October 22, 2009). "PayPal finally poised to enter Web 2.0". San Jose Mercury News.
- Miguel Helft (October 17, 2006). "It Pays to Have Pals in Silicon Valley". The New York Times.
- O'Brien, Jeffrey M. (November 26, 2007). "Meet the PayPal mafia". Fortune (CNN.com). Retrieved December 4, 2009.
- Rachel Rosmarin (July 12, 2006). "The PayPal Exodus". Fortune.
- "Thiel, Levchin and the PayPal Mafia". Fortune. November 15, 2007.
- "More PayPal Mafia Mugshots". ValleyWag.
- "Why Elon Musk isn't in Fortune's PayPal Mafia picture". Valleywag.
- "The Paypal Mafia Personified". Valleywag.
- Marcus Banks (May 16, 2008). "Nonfiction review: 'Once You're Lucky'". San Francisco Chronicle.
- Dylan Tweney (November 15, 2007). "How PayPal Gave Rise to a Silicon Valley ‘Mafia’". Wired.
- O'Brien, Jeffrey M. (November 26, 2007). "Meet the PayPal mafia". CNN Money. Retrieved August 13, 2013.
- Ari Levy (February 21, 2012). "'PayPal Mafia' Gets Richer: Yelp and Facebook's IPOs will give another boost to Silicon Valley's influential PayPal alumni". Bloomberg BusinessWeek.
- David Gelles (April 2, 2015). "The PayPal Mafia’s Golden Touch". New York Times.
- "The PayPal Mafia: Who are they and where are Silicon Valley's richest group of men now?". The Daily Telegraph. Retrieved 2014-09-23.
- J.J. Colao (March 2, 2012). "Aviary is Quietly Cornering a Billion-Dollar Market". Forbes.
- "Tagged.com". Tagged.com. Retrieved August 31, 2013.
- Scott Duke Harris (November 2, 2009). "Greylock raises $575M fund, adds LinkedIn's Hoffman as partner". San Jose Mercury News.
- "Ken Howery « Founders Fund". Foundersfund.com. Retrieved August 31, 2013.
- "Secure.caplinked.com". Secure.caplinked.com. Retrieved August 31, 2013.
- "Rod Martin". Forbes.com. Forbes magazine. Retrieved 14 November 2014.
- "Where Are They Now? The PayPal "Mafia" Is More Powerful Than Ever". BusinessInsider.
- "Dave McClure Hits 500". BusinessInsider.
- "Andrew McCormack Partner". Valar.com. Retrieved September 19, 2014.
- "Luke Nosek « Founders Fund". Foundersfund.com. Retrieved August 31, 2013.
- Sam Biddle (December 4, 2013). "Revealed: A PayPal Mafioso Is Behind "Tips For Jesus" Giving Spree". Valleywag.
- Dan Fost (May 21, 2008). "The Coffee Was Lousy. The Wait Was Long.". The New York Times.
- Sarah Lacy (April 7, 2008). "Something to Yelp About". Bloomberg BusinessWeek.
- "How did Yishan Wong get recruited to PayPal?". Quora.
- Note: links to other company websites and personal home pages may be found on the articles linked to above.