Manchester United have released research which claims that, globally, almost one person in 10 supports the Premier League giants.
The survey, conducted on behalf of the club, shows that the Red Devils have doubled their worldwide support over the past five years.
According to the research, United currently have an estimated 659 million followers - nearly 10% of the Earth's population of seven billion.
Barcelona are United's closest rivals, although the Old Trafford side were shown to have twice the following in Asia.
United's commercial director Richard Arnold said: "Our family of followers has doubled in five years and across the world this represents a very, very important asset and relationship for the club."
The research was undertaken by Kantar, who used a sample of 54,000 people across 39 countries.
Participants were allowed to say that they supported more than one club.