A day after the historic Facebook stock offering, Zuckerberg on Saturday wed 27-year-old Priscilla Chan, his girlfriend of nearly a decade, according to a guest authorized to speak for the couple. The person spoke only on the condition of anonymity.
Zuckerberg gave his new bride a ring he had designed with a "very simple ruby" to end an incredibly eventful week, according to the guest.
The couple married at his Palo Alto, Calif. home in front of fewer than 100 stunned guests who thought they would be attending a party to celebrate Chan's graduation from medical school.
On Monday, Zuckerberg turned 28 and Chan graduated from the University of California, San Francisco School of Medicine, where she'd studied pediatrics.
Then on Friday, Zuckerberg took his blue-and-white web behemoth public in one of the most anticipated IPOs in Wall Street history.
The seemingly well-co-ordinated timing was largely a coincidence, the guest said. The wedding had been planned for months and the couple was waiting for Chan to finish medical school, but the date of the IPO was a "moving target" not known when the wedding was set.
Attendees, including Facebook's chief operating officer Sheryl Sandberg, were told after they arrived that they were not mere party guests but wedding guests.
"Everybody was shocked," the guest said.
The person would not discuss the names of others who attended to protect their privacy.
Ditching his trademark hoodie and sneakers, Zuckerberg sported a dark blue suit and tie with a white shirt for the ceremony, while Chan wore a traditional white wedding dress with veil and lace.
Food was served family-style and included dishes from the couple's favourite Palo Alto sushi restaurant.
Zuckerberg met Chan at Harvard, where he founded Facebook in a dorm room in 2004, and have been together for more than nine years.
Chan's own Facebook page, which now lists her as married to the founder, said she is a native of Braintree, Mass., and attended high school in nearby Quincy.
She graduated Harvard in 2007 then taught science to fourth and fifth graders at the Harker School in San Jose for two years before starting medical school, according to her profile.
Her page also says she "loves cooking and soft things."
Even after the IPO, Zuckerberg, who grew up in Dobbs Ferry, N.Y., remains Facebook's single largest shareholder, with 503.6 million shares, and he controls the company with 56 per cent of its voting stock.
The site has grown into a worldwide network of almost a billion people and made its founder, Time magazine's Person of the Year in 2010, one of the most famous businessmen of the Internet age.
Associated Press Writer Andrew Dalton contributed to this story from Los Angeles.