The Catalan giants overtook Los Blancos, who topped the 2019 Money League, and became the first club to exceed €800 million (£687.3 million) in revenue.
Eight of the top 20 are Premier League sides, while Serie A has the next most representatives with four. There are three apiece from La Liga and the Bundesliga, while there are two entrants from Ligue 1.
Here's the top 20 in full:
Ornella D. Bellia @DesireeBellia
#Deloitte Football Money League 2020 ⚽️📊💰 💰➡️ The ”TOP 20” clubs generated a record of €9.3bn (11% increase). 💰➡️ #FCBarcelona becomes the first club to break €800 m revenue barrier ⚽️➡️ 8 English clubs ⚽️➡️ 4 Italian club ⚽️➡️ 3 Spanish /3 German ⚽️➡️ 2 French clubs https://t.co/APjsIx0mWK
The top 20 also enjoyed a combined revenue increase of €1 billion from last year.
Barcelona's lead over Real Madrid is a record:
Deloitte's Dan Jones told Jamie Gardner of the Press Association (h/t MailOnline) that Barcelona have taken top spot by maximising their commercial revenue, such as merchandising and licensing income.
Jones observed their commercial revenue alone, which totalled €383.5 million (£326.6 million), was higher than 12th-placed Borussia Dortmund's total income.
"With the club expecting further growth of €30 million (£25.5 million) in commercial revenues and total revenue of almost €880 million (£749.5 million) in 2019-20, we expect them to retain the top spot in next year's edition," he added.
Meanwhile, he said United are in danger of being caught by their domestic rivals for the first time:
"United have been the top English club since we started the Money League, but that could come under a bit of pressure when we do it in 2021.
"That will cover this season when Liverpool are having an tremendous season on the pitch, so we think there's a possibility of United losing that No. 1 position."
The Red Devils are projecting a sizeable fall in revenue this season after they missed out on UEFA Champions League qualification in the last campaign:
According to Jones, that loss could see Liverpool or Manchester City leapfrog them if they go deep in the Champions League, which would bring in a great deal of broadcast revenue.
United are under pressure again this season to finish in a Champions League place, as they sit five points outside the Premier League's top four after 22 games.
Arsenal are another English club who have suffered for missing out on Europe's premier competition:
The Gunners have finished outside the top four in each of the last three seasons. They had the chance to secure Champions League football last season by winning the UEFA Europa League, but they lost 4-1 to rivals Chelsea in the final.
The Europa League will be Arsenal's best chance of qualifying for the Champions League this season, too, as they sit 10th in the Premier League, 11 points off the top four.