Mazel tov to Facebook founder Mark Zuckerberg and his longtime girlfriend, med student Priscilla "Cilla" Chan, who are engaged! According to Bill Gates, at least, who seemed to let the news slip during an interview with The Daily Mail:

He is friends with Facebook founder Mark Zuckerberg, 27, who has already pledged to give most of his fortune away. Gates lets slip that Zuckerberg may be engaged to Priscilla Chan, his long-term girlfriend: ‘I didn't say to Mark, "Give me all your money!" He was predisposed to do it and he came to me seeking advice.

'His fiancée Priscilla thought about education and he gave money to Newark, New Jersey, and we did a co-grant so that some of our people who had some expertise in that field could help him out.

Gates could have misspoken, obviously, but the news would hardly be surprising. Chan and Zuckerberg have been dating since 2003, and, more importantly, the pair finally listed themselves on Facebook as being "in a relationship" earlier this year. Plus, the 26-year-old just dropped $7 million on a Palo Alto palace, which is more than enough room for the Zuckerberg-Chans—Mark, Priscilla, and any others that come along.

(Needless to say, if you know any more about Zuckerberg's possible engagement, drop us a line.)

Update: Did Gates misspeak? Business Insider writes:

We checked with Facebook's head of communications, Elliot Schrage, who suggested that Bill Gates was mistaken. "If [Mark is engaged, Bill Gates] knows something I don't know. Gates's communications guy just wrote to apologize for the misunderstanding."

On the one hand, calling Chan Zuckerberg's fiancee is an understandable, even likely, slip. On the other hand, we'd probably tell Bill Gates about our engagement before Elliot Schrage. No offense, Elliot.

[Daily Mail]