Their global appeal is particularly strong in the Far East, where they are mobbed.
And Giggs believes the club's history has captivated fans from all corners of the globe.
He said: "I think there are a lot of things that make Manchester United a special club.
"There's the history - the successes, the Busby Babes, the Munich air disaster, its great players and teams as well as what the club has achieved under Sir Alex Ferguson.
"When all that is added together, it makes United a massive club."