United also remain ranked as the most valuable team in any sport, worth 2.24billion US dollars (?1.4bn), 385million USD more than baseball's New York Yankees and the NFL's Dallas Cowboys.
Arsenal are fourth on the list, worth 1.29billion USD (?800m), behind Real Madrid (?1.6bn) and Barcelona (?816m) but just ahead of Bayern Munich (?766m). Chelsea are in seventh place, worth ?474m, and Liverpool eighth with a value of ?386m.
United's huge global fanbase, estimated by Forbes to number 330million, has helped maintain the club's position at the top. However both Real Madrid and Barcelona have higher revenues than United, due in large part to the fact they have negotiated their own individual television rights deals for Spanish football.
The figures are also based on last year's financial results reflecting United getting to the Champions League final.
This season Sir Alex Ferguson's side failed to make the knock-out stage and their income from European football is expected to suffer a corresponding drop, especially in relation to Real Madrid and Barcelona who are both in the Champions League semi-finals.
Tottenham are 11th on the list, valued at ?351m, and Manchester City 13th, worth ?276m.