For a second straight year, the Spanish giants topped the 30-club list compiled by the American business magazine, with Manchester United second, valued at $6bn (£4.8bn).
This year's list marks the first time that two clubs have reached the $6bn mark. Madrid increased their value in the past year by 19%, while United climbed 30%.
"The Spanish side has made it to five of the last nine lucrative Champions League finals, winning all of them," Forbes said.
"Real Madrid has also secured nearly $400 million from Sixth Street and Legends as part of a 20-year deal to enhance revenue at its Santiago Bernabeu Stadium, which has been undergoing a massive renovation that is expected to be completed next year."
Madrid and United are the only two clubs to have ranked in the top five each year since 2004, when Forbes began publishing annual valuations of football clubs.
Six of the top 10 ranked clubs in the report are Premier League sides, and seven of the top 30 clubs are from Major League Soccer, with LAFC at No. 17 the American side highest on the list.
Forbes' Top 10 Most Valuable Clubs
1. Real Madrid ($6.07bn)
2. Manchester United ($6bn)
3. Barcelona ($5.51bn)
4. Liverpool ($5.29bn)
5. Manchester City ($4.99bn)
6. Bayern Munich ($4.86bn)
7. Paris Saint-Germain ($4.21bn)
8. Chelsea ($3.1bn)
9. Tottenham Hotspur ($2.8bn)
10. Arsenal ($2.26bn)