Facebook has over 845 million users today, with users from over 200 different countries.
The United States with more than 155 million Facebook users continues to be the largest Facebook nation, followed by India at a distant second with about 43.5 million Facebook users.
The country with the smallest user base, according to data from socialbakers, is the Vatican City with 20 Facebook users.
The screenshot below shows the top 25 of the largest Facebook nations as of 3:00 PM GMT, 04 February 2012. Changes in user base are based on the last 3 months.

Check out the full list of Facebook nations at http://www.socialbaker.com/facebook-statistics
Socialbakers.com is one of the biggest social media statistics portals, covering a wide range of social media statistics for the like of Facebook, Twitter, Google+, LinkedIn, and YouTube.
Facebook is on the verge of conquering yet another milestone with its number of users fast approaching the 700-million-users mark.
Facebook’s official statistics list 500 million active users.
But, Facebook stat tracking site Socialbakers says the largest and the most popular social networking site will soon be registering its 700-millionth signup, boosted by huge growth in Brazil, Indonesia, Philippines, Mexico, and Argentina – all of them seeing more than 1 million new signups. Countries like Brazil and Egypt showed huge growth of more than 11% in the last month.
India, Colombia, Egypt, Turkey, and UK closes the top ten list of ‘Top Growing Countries in May 2011 on Facebook”.
The top 5 countries on Facebook (according to number of users) are United States, Indonesia, Turkey, UK, and India.
According to a new Nielson study, if you are additcted to posting updates on Facebook, there’s a good chance you have money and are more urban than your non-facebooking peers.
Facebook users are more affluent than their counterparts on Myspace. And bloggers and Facebook users tend to live in urban areas.
The survey showed that Facebook users generally have an upscale profile. Other recent studies have shown that as Facebook grows in popularity, its user base is growing older.
That means Facebook, which has shown phenomenal growth in the past year, appeals to an older, wealthier demographic.