Facebook now has more than one billion people using it every month, the company has said.
The passing of the milestone was announced by founder Mark Zuckerberg on US television on Thursday.
The company said that those billion users were to date responsible for 1.13 trillion "likes", 219 billion photos and 17 billion location check-ins.
The site, which was launched in 2004, is now looking towards emerging markets to build its user base further.
"If you're reading this: thank you for giving me and my little team the honor of serving you," Mr Zuckerberg wrote in a status update.
"Helping a billion people connect is amazing, humbling and by far the thing I am most proud of in my life."
Statistics released to coincide with the announcement revealed there were now 600 million users accessing the site via a mobile device - up 48 million from 552 million in June this year.
Since its early beginnings at Harvard University, Facebook users have befriended each other 140.3 billion times.
Sustained growth is seen as crucial if Facebook is to maintain its value - the company has seen its share price drop to about $22 (Ł17) from a starting price of $38.
Investors will expect the company to look at ways to make more from the users it already has as well as seeking to attract new users in areas of the world where it does not yet dominate.
"For Facebook the main challenge is not just to grow in terms of numbers, but more importantly to deepen and enrich engagements," said Eden Zoller, principal analyst at tech research firm Ovum.
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