More than a quarter of the world's population, including nearly two thirds of New Zealanders, now use Facebook every month, the social network says.
"As of this morning, the Facebook community is now officially two billion people," founder and chief executive Mark Zuckerberg posted.
The milestone comes just 13 years after the network was founded by Mr Zuckerberg when he was at Harvard.
He famously dropped out of the university after launching the global social-networking website.
The internet giant announced it had one billion monthly active users in October 2012, meaning it has doubled the number of its users in just under five years.
There were currently 2.9 million monthly active users in New Zealand, it said in a statement.
This would be the equivalent of three in every five residents - or nearly two thirds - based on the latest population estimates.
The firm's continuing growth will confound critics who have long predicted that the social network's growth would slow down as rivals such as Snapchat stole its users.
Earlier this year, Facebook warned that growth in advertising revenues would slow down.
Nonetheless, Mr Zuckerberg's ambitions remain huge.
He told USA Today the firm had not made "much fanfare" about hitting the two billion figure because "we still haven't connected everyone".
"What we really care about is being able to connect everyone," he said.
The firm's rapid growth has put pressure on its ability to moderate violent and illegal content posted on its site.
The most recent high profile incident involved a man in the US posting a video of himself to the site, showing him shooting and killing an elderly man.
Last month Facebook said it was hiring 3000 extra people to moderate content on its site.
'Victim of its own success'
Facebook's continued growth was impressive, New Zealand tech expert Paul Brislen said.
"To hit two billion users and to have consistent growth as it is at the moment; having 17 percent growth year on year, growing at fastest rate since 2012 - that is quite remarkable in what I would have thought of as a mature market," he said.
But the social network had become a victim of its own success too, Mr Brislen said.
"My concern is really that Facebook doesn't really know that it is the future of publishing and yet that is exactly what it is. It refuses to play the part of a media publishing house when in fact what it has managed to do is destroy the media publishing business."
And the ease of use meant negative and potentially dangerous communities had just as much of a chance of establishing themselves, and Facebook had done a poor job of policing them, Mr Brislen said.
"Whether its neo-Nazism, actual Nazism, lies about public events, conspiracy theories about the Twin Towers or the Sandy Hook massacre.
"These things grow and flourish because nobody is pulling them up on it and unfortunately Facebook is the only company that can control Facebook posts and it simply abdicates responsibility. I think that is something that is going to be addressed for them, whether they like it or not."
Most of Facebook's growth has been in the developing world and this was due to the popularity of mobile in those regions such as South East Asia, he said.
He said Facebook was now facing a challenge from competing platforms trying to eat into their user base, including Snapchat, WeChat and Google.
- BBC / RNZ