Since the Champions League format was introduced in 1992, no side has managed to retain their European crown.
However, Real Madrid idol Cristiano Ronaldo is confident The Whites can actually pull off this difficult feat - and wants to see a good start on Wednesday at home to Sporting Lisbon, the club where he started his illustrious career back in 2002.
"Sporting mean a lot to me, it is where I started out, but now I'm wearing the colours of Real Madrid and I want to win. It will be a special match, and a privilege for me to face Sporting," he said.
"To win back-to-back Champions titles is a massive challenge for us. But Real Madrid are always one of the candidates.
"We know it is going to be very complicated but we are going to try. We will take it match by match, hoping to make a good start on Wednesday.
"It will not be an easy group, but we have to think positively: it is possible for us to win it again."
The other two rivals for Real in Group F are Borussia Dortmund and Legia Warsaw.
Ronaldo, 31, has cleverly learned how to deal with becoming a veteran. He no longer attempts those 40-metre dashes of his Sporting, Manchester United and early Real days.
Instead, he now plays as a false left-winger, cutting inside to have a shot with his right foot or to take a centre from the likes of Gareth Bale and Dani Carvajal.
"He is a more limited but also more intelligent player than a few years ago," commented Madrid radio Cadena SER.
"He has learned how to ration his physical efforts, saving himself for the final few metres."
Ronaldo made a successful return from injury in Saturday's 5-2 slaughter of Osasuna, making it 1-0 by turning in a centre from Bale after just six minutes.
He is poised to extend his contract with The Whites for five more years, though he has said. "I think a 10-year extension would be more appropriate. I feel wonderful and I'm sure I can continue playing until 40 at least."
He has won the Champions League three times: 2008 with United, and 2014 and 2016 with Real. Ronaldo is the all-time leading Champions League scorer with 94 goals and has the sixth-most appearances with 131 games.
Last season with very special for him, he says, with not only Real winning their 11th Champions but also with his beloved Portugal prevailing at Euro 2016 against all the odds.
"In terms of title it was possibly the best season of my career. I have never enjoyed a better season."
Not since 1960 have Real succesfully managed to defend their European crown. Indeed, they have never reach the final when defending champions.
However, this year might be different - if Ronaldo manages to continue holding back they years.