They are the two most valuable clubs in soccer, and on Wednesday they'll go head to head in the first leg of this season's most glamorous Champions League Round of 16 tie.
Manchester United, who last month became the first sports club to be valued at more than $3 billion by Forbes, has been atop the ranking in each of the six years the data has been published, and on all six occasions Real Madrid -- worth approximately $1.9 billion according to 2012 estimates -- has come in second.
Champions League revenue represents a significant portion of the income base for both clubs (UEFA splits more than $1.2 billion between the participating sides), so needless to say neither will want to go out of the competition this early.
But unless you're a bean-counter at Old Trafford or the Bernabeu money will be of only peripheral significance when United and Madrid lock horns on Wednesday, and again on March 5. The route to such riches, after all, begins with success on the pitch, and few sides have been more successful than these two in recent times.
And yet, theirs is a rivalry more fanciful than actual. United and Madrid have faced one another only eight times previously, and never in a major final. United has never won in four attempts at the Bernabeu, and the all-time record bends slightly toward Madrid, who have three wins, two losses and one draw.
If there is some common history to be found between the biggest names in the sport it goes back to their first four meetings. In 1957, a Madrid side led by the great Alfredo di Stéfano beat Duncan Edwards and the Busby Babes 5-3 over two matches in the semifinals.
A year later much of that United team, including Edwards, had perished in and following the Munich Air Disaster, and it wasn't until 1968 that they'd see one another again.
That year Matt Busby's rebuilt side handed Madrid a 1-0 defeat at Old Trafford thanks to a George Best goal, and they progressed to the final following a 3-3 draw at the Bernabeu in the return leg, where David Sadler and Bill Foulkes scored five minutes apart midway through the second half to pull United level.
Three of the four times United and Madrid have been drawn together in the knockout stages of this competition one of them has gone on to lift the European Cup. That's one of the storylines that will be talked about in the run-up to Wednesday's kickoff (1:30pm, Sportsnet), but there are a few other ones as well:
-- The two managers -- United's Sir Alex Ferguson and Madrid's José Mourinho -- have a fascinating relationship.
Mourinho has always been very public about his admiration for Ferguson, and it has long been thought the United boss would like his Madrid counterpart to succeed him at Old Trafford when he retires.
While at Chelsea, Mourinho's teams lost only one of 10 matches against Ferguson's, but in the Champions League each has one win, one loss and two draws in four meetings.
-- Cristiano Ronaldo played for Manchester United from 2003 to 2009, in which time he helped the Red Devils to three Premier League titles and the 2008 Champions League crown.
That same year he became the club's fourth player -- and first since George Best -- to win the Ballon D'Or. He'll return to Old Trafford on March 5 in Madrid colours, having moved to Spain for a world-record fee in 2009.
-- Recent form. United is perched comfortably atop the Premier League table and has a nine-point lead on second-place Manchester City after 25 matches.
The team is unbeaten in its last 13 matches in all competitions heading into the weekend but has kept only four clean sheets in that stretch. Madrid, meanwhile, has struggled in La Liga and is a disappointing third in the standings -- a whopping 16 points adrift of Barcelona. It goes into the weekend on the back of a loss to Granada and is without No.1 goalkeeper Iker Casillas.
Projected Manchester United XI: De Gea; Rafael; Ferdinand, Vidic, Evra; Carrick, Giggs; Kagawa, Rooney, Welbeck; Van Persie
Projected Real Madrid XI: Lopez; Arbeloa, Ramos, Pepe, Coentrao; Khedira, Alonso; Di Maria, Ozil, Ronaldo; Benzema
Projection: Manchester United progress on aggregate.