Teenage substitute Mezian Soares gave Lens a 1-0 win over Nantes in Ligue 1 on Friday to give his side direct qualification for next season's Champions League while relegating Nantes to the second tier.
The result also keeps the Ligue 1 title race alive with Lens the only team who can still pip Paris Saint-Germain to the title.
After a frantic and eventful first 79 minutes, the 16-year-old Soares picked up a loose ball in the box and fired home to break the deadlock.
Lens are now guranteed a top-two finish in Ligue 1: they are seven points clear of third-placed Lyon with both teams having two games left.
Third place also earns a place in the Champions League but in the play-off third round.
Lens, whose budget is not even a 10th of Champions League finalists PSG, are still to play the Parisians who lead them by three points and have a game in hand.
Nantes held a marauding Lens at bay largely thanks to 'keeper Anthony Lopes, who produced a string of saves as Lens had three goals ruled out for off-side or handball.
French champions in 2001 Nantes are now guaranteed to finish in the bottom two and will be relegated from Ligue 1 for the third time since their title win.
PSG play Brest at home on Sunday.