Mark Zuckerberg and Pricilla Chan May 2012 Wedding (Photos) ~ Purlzek

Zuckerberg (28) tied the knot with his girlfriend Priscilla Chan (27) in a simple ceremony held in their backyard Saturday. The multi-billionaire placed a simple "ruby sparkler" in Chan's finger in the ceremony which was attended by less than 100 guests in Palo Alto, California.

The wedding came as a surprise to the guests as they thought they were attending a party to celebrate Chan's graduation from the UCSF medical school. The guests were informed about the marriage after they arrived at the event.

Zuckerberg met Chan in Harvard in 2003 before he co-founded Facebook in 2004 and they had been dating for the last nine years.

Chan, born in Braintree in Massachusetts, did her schooling at Quincy High School and worked at FASE as director/mentor before completing her graduation from Harvard in 2007, according to her Facebook profile. For a year, she worked as a teacher at the Harker School and later joined the UCSF for her medical education.