The 19-times English champions, who are preparing for a listing on the New York Stock Exchange, were valued at US$2.23 billion - that's £1.43 billion - 19 per cent above Real Madrid.
But while United may have been eclipsed in the league last season by their fierce rivals Manchester City, City is still a strictly second division club when it comes to financial clout - notwithstanding the wealth of the side's owners, of course. The Premier League champions did not even crack the top 50.
All 32 NFL franchises made the top 50 list with the Dallas Cowboys, Washington Redskins, New England Patriots and Super Bowl champion New York Giants all securing spots in the top 10.
The only teams in the top 10 that do not play football or American football were Major League Baseball's New York Yankees, who were tied at third with the Cowboys, and the Los Angeles Dodgers, who were tied with the Patriots at number.
The top 50 list included seven football teams, with Arsenal falling three places to 10th overall and Barcelona rising 18 spots to eighth.
Ferrari was the top motor racing team, listed at 15th, while the LA Lakers, in 30th place, were the highest-placed NBA franchise.
Top 10 teams:
1. Manchester United (Football) - $2.23 billion
2. Real Madrid (Football) - $1.88 billion
T3. New York Yankees (MLB) - $1.85 billion
T3. Dallas Cowboys (NFL) - $1.85 billion
5. Washington Redskins (NFL) - $1.56 billion
6. Los Angeles Dodgers (MLB) - $1.40 billion
6. New England Patriots (NFL) - $1.40 billion
8. Barcelona (Football) - $1.31 billion
9. New York Giants (NFL) - $1.30 billion
10. Arsenal (Football) - $1.29 billion
11. Bayern Munich (Football) - $1.23 billion
15. Ferrari (F1) - $1.1 billion
27. AC Milan (Football) - $989 million
30. LA Lakers (NBA) - $900 million
40. McLaren (F1) - $800 million
45. Chelsea (Football) - $761 million