They're also the defending Liga champions and an economic juggernaut that boasts one of the two best players in the world (and a gaggle of superstars beyond him), as well as a manager who thus far has barely put a foot wrong and who seems tailor-made for them.
So if those are the ingredients for a dynasty, who is best placed to unseat them?
Take this exercise for what it is: a bit of crystal ball juggling. And bear in mind, we're at the start of the summer transfer window. Tons can, and probably will, happen.
Another caveat: we're not talking about who "can" win the Champions League next year. Nor is it simply about unseating Real Madrid. We're talking about who (if anyone) is best placed to build sustained European and domestic success over the next few years. This doesn't just mean building a great side and delivering silverware; it means having the clout to retain talent, both playing and managerial. And it means being able to deliver domestically on a regular basis as well.
WHY THEY WILL: They're a major club with a big stadium in a major city where it's easier than elsewhere to attract talent. Arsene Wenger has told us endlessly that there's plenty of money to spend.
WHY THEY WON'T: For a start, they're a year behind schedule in that they won't even be in the Champions League until 2018-19 at the earliest. And there's plenty of competition for places in the Premier League, which doesn't help. Wenger turns 68 in October and continues to divide opinion. The future of two of their biggest stars, Alexis Sanchez and Mesut Ozil, remains in limbo. And even if they stick around, this still feels like a long-term project. Historically, have had serious issues retaining their major stars.
WHY THEY WILL: They're an economic juggernaut and one of the best brands in the game. They have Lionel Messi and a stellar supporting cast, both in terms of production and star power. Spanish clubs tend to do well in European competition.
WHY THEY WON'T: Messi has yet to extend his contract, which expires in just over a year's time. You assume he will, but until that happens, there's uncertainty. Their new boss Ernesto Valverde has been coaching for 15 years and is only just now ascending to a mega-club. It's not lost on anyone that their recent success has come with "philosopher-king" types like Pep Guardiola and Luis Enrique in charge, rather than more pragmatic guys (Tata Martino, anyone?). There is still some important strengthening to be done in key roles.
WHY THEY WILL: They dominate the Bundesliga and have reached the Champions League quarterfinals in five of the past six seasons. Together with Manchester United, Barcelona and Bayern, they're one of the quartet of clubs that are far ahead of everyone else commercially. They can vacuum up talent domestically whenever they like. No coach has won the Champions League more times than Carlo Ancelotti and the Bundesliga's winter break is a boon to clubs in European competition.
WHY THEY WON'T: Most of their key performers are 28 or older, which means this feels like a team of the present more than one of the future. It's unclear how much steamrolling the Bundesliga helps you succeed in Europe. Over the next year or so, they'll need to replace Xabi Alonso, Philipp Lahm, Arjen Robben and Franck Ribery, which means there's a lot that can go wrong.
WHY THEY WILL: Antonio Conte has managed for six full seasons with four different clubs and won the league in five of those six. (The one time he didn't win, with Siena in Serie B, he finished second and won promotion). No English club has won more trophies in the Roman Abramovich era. They're expanding their grounds and that will generate even more revenue. Eden Hazard is a genuine superstar, ready to go to the next level.
WHY THEY WON'T: Conte's record in knockout competitions is comparably humdrum. They need to add serious depth now that they're playing in Europe as well. Diego Costa is hit or miss and will reportedly leave. Hazard is injured and perpetually linked to moves elsewhere. The redeveloped Stamford Bridge won't be ready until 2023 and they face several seasons at Wembley (never a good thing) in between.
Juve are facing more competition in Italy but are they strong enough to keep their stars and win in Europe?
WHY THEY WILL: They've come within 90 minutes of winning it all twice in the past three seasons. They have a revenue-generating stadium and a strong brand that can still be better commercialized. Max Allegri is a clever manager who has just re-committed himself to the club for the long term. Qualifying for the Champions League won't be an issue. And while the squad isn't young, they've already secured some very promising talent (Riccardo Orsolini, Marko Pjaca, Mattia Caldara, Daniele Rugani, Paulo Dybala...)
WHY THEY WON'T: Ten of the 14 players we saw in Cardiff will be the wrong side of 30 by the end of next season. As good as the kids might be, their window of opportunity is now, not in a few years' time. While this season offered a little bit more of a challenge domestically, Serie A doesn't do much in terms of toughening you up for European competition. The departures of Paul Pogba, Alvaro Morata, Arturo Vidal and Carlos Tevez in recent years suggest talent retention isn't that easy for them.
WHY THEY WILL: Jurgen Klopp is hugely popular and hugely admired. He has total buy-in from the fan base. Liverpool are a very solid brand; they continue to grow commercially and have expanded their stadium. This will be Klopp's second full season and the one where you expect to see a great leap forward in terms of tactics and chemistry.
WHY THEY WON'T: For all their storied history, they've only finished in the top four twice in the past eight seasons and the Premier League isn't getting any less competitive. They still can't match the very big boys in terms of buying power, and the Fenway Sports Group have shown little appetite for massive spending. There are still plenty of holes to plug in the squad. Talent retention might be a problem going forward.
WHY THEY WILL: Pep Guardiola helped build the last dynasty at Barcelona, and his brand of football has proved successful in the past. He's been in the Champions League eight times and has advanced to the final four on seven occasions. They've shown a willingness to spend, and while they probably can't outspend their crosstown rivals Manchester United over time, for now they feel they're a match for anyone. They skew young, and they're entertaining to watch.
WHY THEY WON'T: The learning curve has been really steep in year one of Guardiola's Premier League career, particularly in the field of goalkeepers and defenders. Who's to say he won't repeat the same mistakes? They need more and better investment this summer, ideally guys who can satisfy the homegrown player requirement. And again, a top four finish in England is not something you can take for granted.
Pep Guardiola is successful at building dynasties, but his City squad need a significant overhaul.
WHY THEY WILL: They're a gigantic cash cow, topping the Deloitte Football Money League of the world's richest clubs and raking in some $300 million more than the next highest Premier League club. That means resources aren't a problem. Jose Mourinho has won the Champions League with two different clubs and conquered a European trophy just last year. They have a decent core of talent to rally around and a fan base hungry for success.
WHY THEY WON'T: They finished 34 points off the pace last season and Zlatan Ibrahimovic, the guy who scored nearly a third of their goals (while missing more than a fourth of their league campaign), is injured and may never play for them again. Mourinho himself said he needs several more transfer windows to get the squad he wants. Rebuilding United in his image is a slow burner, and by the time they're ready, someone else may have snatched the dynasty tag.
WHY THEY WILL: They're the only show in town in one of Europe's biggest and most glamorous (not to mention wealthiest) cities, and they have deep-pocketed owners. Qualifying for the Champions League is virtually automatic. Despite domestic disappointment last year, the squad is already very strong.
WHY THEY WON'T: Unai Emery was disappointing in his first season and doesn't seem like the kind of guy you associate with dynasties. They have tons of money, but they don't seem to spend it particularly well. For too many of their guys, PSG feels like either a stepping-stone or a payday rather than a long-term destination.
WHY THEY WILL: Mauricio Pochettino is one of the most coveted managers out there, and they have exciting young attacking talent while being taught at the back, which is never an easy combination. They are London-based, so they're attractive to some of the pickier overseas players, and their new stadium is bound to boost revenue.
WHY THEY WON'T: Talent retention has been an issue in the past. And while it's hard to see Harry Kane ever playing for anybody else, you'd imagine clubs will come calling for Pochettino, Dele Alli and others. They were disappointing at Wembley, last year and the prospect of playing a whole season there isn't great. It still feels like ownership wants to boost revenue first and spend big later, which could be problematic at this level.