A surge in the club's shares after a poor start when they were offered on the New York Stock Exchange in August has seen the overall value of United rise to 3.3billion US dollars (£2.1billion).
According to Forbes, United are comfortably ahead of the world's second-most-valuable sports team, the NFL's Dallas Cowboys, worth 2.1billion dollars (£1.4billion).
The United shares were initially offered to the public at 14 dollars and are now worth just under 17 dollars.
It means a huge increase in the overall wealth of the Glazer family, who have a controlling interest in United, and billionaire investor George Soros - the 22nd richest person in the world - who bought a 7.5 per cent stake in the club.
United's commercial growth appears to be driving the share price up, with the club announcing several new sponsorship deals since August, qualifying for the Champions League knockout stages, and with the prospect of the new bumper Premier League television deals that are coming on stream from August.
The Glazers sold 10 per cent of their shares in the initial public offering sale in August but United's vice-chairman Ed Woodward insisted in October the family will not sell the club for "many, many years" despite ongoing interest.
Woodward said they had no interest in cashing in the rest of their holding.