Mark Zuckerberg
Mark Zuckerberg is the film's protagonist. A brilliant Harvard sophomore who is unapologetically arrogant, Mark is driven to gain power and respect through the creation of his social networking website. In the quest to make Facebook popular, he makes unethical choices that involve the betrayal of friends and intellectual property theft. At the end of the film, Mark has become the youngest billionaire in the world. However, he remains a solitary figure who longs for social acceptance.
Eduardo Saverin
Eduardo Saverin is a fellow Harvard student and one of Mark's closest friends. Mark goes to him with the idea for The Facebook and Eduardo invests $1,000, becoming CFO. Eduardo and Mark's relationship becomes strained as the company grows, with Mark leaving Eduardo out of most business decisions. Eduardo freezes the Facebook bank account to get Mark's attention. Mark retaliates by creating a newly incorporated company that issues new shares that dilute Eduardo's stake significantly. Eduardo sues Mark. At the end of the film, Mark agrees to an undisclosed settlement and Eduardo is restored to the masthead of Facebook as a cofounder.
Sean Parker
Sean Parker is a brilliant but no-longer-successful founder of the file-sharing website Napster. He is popular with women and confident in demeanor. He recognizes Facebook's potential and convinces Mark to move to California. Against Eduardo's wishes, Mark hires Sean as president of Facebook, and Sean arranges an investment from Peter Thiel. At the end of the film, Sean is caught doing cocaine with underage Facebook interns.
Cameron and Tyler Winklevoss
Cameron and Tyler Winklevoss are identical twin athletes who competitively row for Harvard. They hire Mark to build their exclusive dating website, TheHarvardConnection.com. They grow incensed when they learn that Mark has been stalling on them while simultaneously building Facebook, a social networking website based on a similar premise to their website. They are initially reluctant to sue him because they see themselves as principled "Harvard gentlemen." However, they eventually sue Mark and are given a $65 million settlement.
Divya Narendra
Divya is a friend and business partner of the Winklevoss Twins. He is one of the founders of TheHarvardConnection.com, a dating website that Mark was supposed to build.
Erica Albright
Erica Albright is Mark's girlfriend at the beginning of the film. She breaks up with him after he insults her by saying that she will get to meet people she wouldn't otherwise mix with if he gets into a final club. Erica tells him he will become a successful computer person but that everyone will hate him because he's an asshole. At the end of the film, Mark sends her a Facebook friend request.
Larry Summers
Larry Summers is the president of Harvard University. When the Winklevoss Twins go to Summers to complain about Mark stealing their idea, Summers is completely unwilling to get involved in the dispute. Rather than help, he tells the twins to come up with another idea.
Marilyn Delphy
Marilyn Delphy is one of the junior lawyers working for Mark. She speaks to Mark several times during recesses in his depositions. At the end of the film, she tells him that it will be easier for him to pay out the people suing him rather than go to trial. She also tells him that he isn't an asshole, he's just trying hard to be one.
Christy
Christy is Eduardo Saverin's girlfriend. She meets Eduardo and Mark during a lecture given by Bill Gates. She impresses Eduardo when she asks him to "Facebook" her later to set up a time to get together. Later in the film, she becomes intensely suspicious of Eduardo, who seems afraid of her volatile emotional state. The couple breaks up when she sets fire to a scarf he brought her from New York.
Peter Thiel
Peter Thiel is a billionaire cofounder of PayPal. In the film, Thiel agrees to give the fledgling Facebook $500 million in startup cash as an "angel investor" who will have a 7% stake in the company. He also instigates relocating the company to Delaware for tax reasons.
