Kingsley Coman’s low volley helped Bayern Munich gain advantage over his former club Paris St-Germain in their last-16 first-leg tie.
Coman also scored the only goal when Bayern overcame his former club PSG to win the trophy in 2020.
PSG were boosted before the game with Lionel Messi fit enough to start up front after recovering from a hamstring injury and Kylian Mbappe okay enough to be on the bench.
France forward Mbappe looked to have rescued a draw for the hosts, but his late effort was ruled out for offside in the build-up with the aid of the semi-automated offside technology.
A bright moment on the night for the Parisiens was a start in midfield for Warren Zaire-Emery who, at 16 years and 343 days, became the youngest player ever to start a Champions League knockout stage game.
The Frenchman was born in 2006, the same year in which Messi, 35, won his first Champions League title.
While Bayern are unbeaten in all competitions since 17 September and now have the advantage going into the second leg despite having defender Benjamin Pavard sent off for a second booking in injury time, Ligue 1 champions PSG have now lost their last three matches in all competitions.
Following losses to Marseille in the Coupe de France and Monaco in Ligue 1, another damaging defeat piles the pressure on manager Christophe Galtier.
PSG, who have still never won the Champions League, now face a tough task in the return leg in Germany on 8 March.