Facebook founder and chief executive Mark Zuckerberg updated his status to "married".
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.
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 featuring "a very simple ruby" that he designed himself.
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 IPO, Zuckerberg remains Facebook's single largest shareholder, with 503.6 million shares. He controls the company with 56% of its voting stock.
The site, which was born in a dorm room eight years ago and has grown into a worldwide network of almost a billion people.
Zuckerberg founded Facebook at Harvard in 2004.
He was named as Time's Person of the Year in 2010, aged 26.