Norwegian international Guro Reiten's first-half goal gave Chelsea a 1-0 win away to holders Lyon in France in the first leg of their Women's Champions League quarter-final tie on Wednesday.
Reiten curled a first-time effort low beyond goalkeeper Christiane Endler just before the half-hour for the visitors, a fine finish coming after an outstanding piece of play by Scotland's Erin Cuthbert to create the chance.
The result puts Emma Hayes's Chelsea — runners-up two years ago — in the driving seat as they seek to become the first English winners of the competition since Arsenal in 2007.
"A 1-0 win at the home of the reigning champions to take into the second leg, I can't ask for any more," said Hayes.
"We were really compact and defended well. But we're only halfway there."
Chelsea had already beaten France's other heavyweight, Paris Saint-Germain, home and away in the group stage, yet Lyon's pedigree in Europe is second to none.
Lyon won the title last year for the sixth time in the last seven seasons, and Sonia Bompastor's team will still hope to turn this tie around in next week's return.
"I am really frustrated with the result and that the team were not more clinical," admitted Bompastor.
"I have confidence in my players for the second leg because they have experience and they have quality.
"We are capable of going there with the ambition of winning. We showed that in the group stage when we beat Arsenal 1-0 after losing 5-1 here."
The visitors could have been further in front before the interval, with a Lauren James shot coming back off the post.
Yet Lyon had chances too, despite former Ballon d'Or winner Ada Hegerberg being left on the bench as she recovers from her latest long injury lay-off.
Delphine Cascarino hit the woodwork in the second half for Lyon, who have won the Champions League a record eight times overall.
Elsewhere, PSG also went down 1-0 at home, as a second-half Dominique Janssen penalty gave Wolfsburg the victory at the Parc des Princes.
A game of few chances came to life just after the break when PSG were awarded a spot-kick for a challenge on Sakina Karchaoui, only for the English referee to decide after a VAR review that there was in fact no foul.
Moments later a handball at the other end by Paris defender Elisa De Almeida was given as a penalty following a VAR check after initially being missed by the officials.
De Almeida, already on a yellow card, was sent off for a second caution before Janssen tucked in the penalty and Wolfsburg saw the game out.
On Tuesday, Barcelona, who won the title in 2021 and were runners-up last season, won 1-0 away to Roma in Italy thanks to a solitary strike from 19-year-old Salma Paralluelo.
Lea Schueller scored the only goal as Bayern Munich beat Arsenal 1-0.