Manchester United were outclassed as Spanish and European champions Real Madrid retained the Uefa Super Cup victory in a sweltering Skopje.
Madrid dominated from the start and deservedly led when Casemiro – who looked offside – slid in a half volley.
They doubled their lead when Isco calmly slotted in from eight yards after a neat one-two with Gareth Bale, who started ahead of Cristiano Ronaldo.
New £75m striker Romelu Lukaku tapped in before Marcus Rashford scuffed wide.
The Europa League winners were given encouragement by Lukaku’s strike, despite rarely threatening the Madrid goal in the previous hour, and could have scored a barely deserved equaliser through half-time substitute Rashford with nine minutes left.
United were unable to create another clear-cut chance as Madrid became the first team to retain the Super Cup since 1990.
With temperatures over 30C in the Macedonian capital, the match was twice stopped for scheduled cooling breaks implemented by governing body Uefa.
The Red Devils have spent £146m this summer on Everton striker Lukaku (£75m), Chelsea midfielder Nemanja Matic (£40m) and Benfica defender Victor Lindelof (£31m) as they look to improve on a disappointing sixth-placed finish in the Premier League last season.
All three new signings started as Mourinho named a strong side against the European champions.
Only Ronaldo was missing from the Madrid team which started their victory against Juventus in the Champions League final, providing a stern test for Mourinho’s new-look side.
But United struggled against the continent’s best, particularly in the first half, as Madrid controlled the tempo with their crisp and purposeful passing.
The English side were unable to effectively keep possession before half-time – managing just 39% of the ball – and mustered only one shot on target when Lukaku headed straight at Madrid keeper Keylor Navas.
Mourinho introduced teenager Marcus Rashford as a half-time substitute, looking to stretch the Spanish club – who the Portuguese boss managed between 2010 and 2013 – on the break.
Although the Red Devils did improve in the second half, they still looked well short of being able to compete with Europe’s most talented sides going into their return to the Champions League this season.
Madrid continued to create chances throughout. Bale smashed against the bar when the score was 2-0, while David de Gea also produced superb saves to stop Toni Kroos, Karim Benzema and Marco Asensio.