Jude Bellingham scored an injury-time tap-in as Real Madrid left it late to beat Champions League debutants Union Berlin at the Santiago Bernabeu.
Bellingham's strike was his sixth goal in six matches for Madrid since joining Los Blancos this summer.
Federico Valverde's 94th-minute shot deflected into the path of the England midfield who tapped into an empty net.
Union, in their first Champions League match, were unable to respond with just one minute remaining.
Carlo Ancelotti chose to play Jude Bellingham in a more advanced number 10 role, and the former Borussia Dortmund and Birmingham City star once again excelled.
He was integral to the Spanish La Liga side's creativity in attack as they racked up 22 shots to their opponent's three.
And, for the third time already in his Real career, the 20-year-old netted a winner for Los Blancos inside the final 10 minutes.
Indeed, without Bellingham's goals Real Madrid would be nine points worse off just six matches into the season.
Real Madrid were deserved winners, having twice hit the post in the second half, although Union looked set for a fairytale draw at the home of the record 14-time winners.
The hosts, semi-finalists in last season's competition, started brightly as Joselu headed Bellingham's teasing cross over the bar.
But Ancelotti's side failed to kick on in the first period, although they themselves were rarely threatened by the visitors.
In the second half, Real were a team transformed as Lucas Vazquez crossed for Rodrygo who struck the outside of the post in the 51st minute with an acrobatic effort.
Nine minutes later, Union keeper Frederik Ronnow tipped Joselu's header on to the woodwork.
Ronnow also made a series of fine saves to keep out Rodrygo and Luka Modric, while Joselu poked a late volley narrowly wide.
But, in the final minute of injury time, Union Berlin failed to deal with a short corner and Valverde's hopeful shot ricocheted into the path of Bellingham, who rolled the ball in from two yards out.
Union, who five years ago were playing in the second tier of German football, will hope to bounce back when they host Sporting Braga in their next Champions League Group C match in 13 days' time.
Real Madrid travel to face Napoli on the same day.
Source: BBC