The hosts got off to a bright start with Mbappé sending an acrobatic attempt wide, but there was also disappointment when Trent Alexander-Arnold was forced off injured.
They still didn’t slow down at all, as by the 10th minute they had seen Franco Mastantuono hit the post and two Rodrygo efforts saved by Gerónimo Rulli, who then came out and spread himself brilliantly to deny Mbappé.
There was a reminder of Les Olympiens’ threat, though, as Timothy Weah came agonisingly close to picking out the top corner.
Marseille then stunned the Santiago Bernabéu in the 22nd minute, when Mason Greenwood pickpocketed Arda Güler and teed up Weah for the wideman to fire past Thibaut Courtois.
Weah forced Courtois into action with a driven strike from range shortly after, but Geoffrey Kondogbia offered Real the opportunity for a swift equaliser when he dangled out a leg to foul Rodrygo and concede a penalty that Mbappé clinically converted.
Rodrygo soon came close with a curling attempt, and Rulli tipped an Aurélien Tchouaméni strike over the crossbar, before Pierre-Emerick Aubameyang hit the side netting at the other end. Rulli also made vital stops to deny Mbappé and Mastantuono before the break.
Los Blancos re-emerged from half time on the front foot, and Mbappé’s shot deflected onto the crossbar by an outstretched boot from Aubameyang, who then tested Courtois with a powerful strike at the other end.
There was a lull after that period, and Real’s cause wasn’t helped by Dani Carvajal petulantly getting himself sent off in the 72nd minute for headbutting Rulli.
There was an even bigger disaster for Marseille, though, as Facundo Medina handled the ball while challenging Vinícius Júnior to concede another penalty, which Mbappé just about snuck through Rulli’s grasp.
Late on, Greenwood had one attempt denied by Courtois and sent another comfortably over the crossbar, as Real Madrid successfully translated their perfect start in LaLiga to the UCL.
In contrast, the disappointment of a defeat on the road is becoming familiar for Marseille, who have also lost away against Stade Rennais and Olympique Lyonnais this term.
Flashscore Man of the Match: Kylian Mbappé (Real Madrid)