The value of Real, a Spanish club owned by its thousands of members, surged 76 percent to $3.3 billion from a year ago, Forbes said in a statement.
United, who have won the English title a record 19 times and are controlled by the American Glazer family, rose 42 percent to $3.2 billion but dropped to second on the list for the first time since Forbes began tracking football finances in 2004.
Real's Spanish rivals Barcelona ($2.6 billion), England's Arsenal ($1.33 billion) and German side Bayern Munich ($1.31 billion) rounded out the top five.
The top 20 teams are worth an average of $968 million, an increase of 26 percent over last year, Forbes said.
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