Ada Hegerberg scored her 60th Women's Champions League goal as Lyon opened their campaign with a nine-goal demolition of Slavia Prague.
Kadidiatou Diani and Vanessa Gilles scored two apiece as their dispirited hosts offered little in response.
Hegerberg's milestone goal came in only her 62nd Champions League appearance.
The Norwegian became the tournament's top scorer in 2019 when she broke the previous record of 51 held by Germany's Anja Mittag.
Sara Dabritz opened the scoring for eight-time champions Lyon inside three minutes before Danielle van de Donk poked in from close range to double their lead in Prague.
Four headed goals before half-time followed - from Gilles, Eugenie le Sommer and Diani's double - as the Czechs struggled to deal with Lyon's aerial threat.
After the break, Hegerberg converted from the penalty spot after she was pulled back in the area by Diana Bartovicova.
Amel Majri made it eight with an easy finish from a Van de Donk ball, before Gilles headed in her second with 10 minutes remaining.
"I am really satisfied how we started off, with the result and with the way we performed tonight," said Sonia Bompastor, head coach of Division 1 Feminine leaders Lyon.
"Maybe we faced a less experienced team, but I am still proud of my side. We kept to our plan and scored a few beautiful goals. Despite the result, there are still things we might improve."
Lyon, who hold the record for Women's Champions League titles, next face Austrian side St Polten on 22 November.
In Tuesday's earlier Group B match, St Polten were beaten 2-1 by Brann on the Norwegian club's Champions League group stage debut.
After a goalless first half, Rakel Engesvik opened the scoring for Brann before Maria Mikolajova equalised for St Polten with a stunning long-range effort.
Natasha Anasi headed in Brann's winner 11 minutes from time with her first goal for the club.