Nantes won the French Cup for the first time in 22 years on Saturday, beating Nice 1-0 in the final at the Stade de France.
Ludovic Blas drilled home a penalty at the start of the second half to bring Nantes the club's first major trophy since winning the Ligue 1 title in 2001.
For much of the season, Nice, owned by Ineos, the group chaired by Monaco-based British petrochemicals billionaire Jim Ratcliffe, looked certain to qualify for the Champions League but, after a recent stumble, could miss out on Europe altogether.
Nantes, who only avoided relegation in a play-off last year, lifted the French Cup for the fourth time and qualified for Europe for the first time in two decades, earning a place in the Europa League.
After the two finals played in an almost entirely empty stadium due to the pandemic, a sell-out crowd of around 80,000 packed the Stade de France -- roughly two-thirds Nantes supporters.
Nice knocked out Paris Saint-Germain and Marseille en route to a first final since 1997, but struggled to create chances with Amine Gouiri and Kasper Dolberg both without a goal in the league since January.
Nice goalkeeper Marcin Bulka, the PSG loanee who helped dump out his parent club on penalties in the last 16, smothered well as Blas darted into the box, with Gouiri then having a shot deflected wide in a gritty first half.
A first final without PSG since 2014 burst into life 15 seconds after half-time when Hichem Boudaoui was harshly penalised for a handball as he attempted to block Quentin Merlin's cross.
Blas hammered the resulting spot-kick past Bulka, sparking euphoric celebrations from the Nantes players and fans.
Pedro Chirivella nearly grabbed a second as he blasted just wide following a corner. Jordan Lotomba made a crucial block to deny Moses Simon from Randal Kolo Muani's cutback.
Nice's best opportunity came with 20 minutes to play as Alban Lafont palmed away from Gouiri before Nantes defender Andrei Girotto produced a superb goal-line clearance to thwart Andy Delort.
Having departed Lille after leading them to the Ligue 1 crown last season, Christophe Galtier's first season in charge of Nice is destined to end in disappointment.