Zuckerberg and 27-year-old Priscilla Chan tied the knot at a small ceremony at his Palo Alto, California home, capping a busy week for the couple.
Zuckerberg took his company public in one of the most anticipated stock offerings in Wall Street history on Friday.
And Ms Chan graduated from medical school at the University of California, San Francisco, on Monday — the same day Zuckerberg turned 28.
The couple met at Harvard and have been together for more than nine years.
A company spokeswoman said Zuckerberg designed the ring himself, featuring “a very simple ruby”.
The ceremony took place in Zuckerberg’s backyard before fewer than 100 guests, who all thought they were there to celebrate Ms Chan’s graduation.
Even after the initial public offering, Zuckerberg remains Facebook’s single largest shareholder, with 503.6m shares. And he continues to control the company with 56% of its voting stock.
The social networking site, which was born in a college dorm room eight years ago, has grown into a worldwide network of almost 1bn people.
Zuckerberg founded Facebook at Harvard in 2004.
He was named Time’s Person of the Year in 2010, aged just 26.