Paris Saint-Germain lost for the first time in any competition since March 20 last year when they were defeated 3-1 at Lens on Sunday.
Lois Openda scored one and set up another as Lens, who have only lost once in Ligue 1 this season, closed the gap on PSG at the top to four points after 17 rounds.
PSG’s last loss was more than nine months ago when they fell 3-0 at Monaco in Ligue 1, although that still left them 12 points clear at the top of the table.
On Sunday at Lens, PSG were without World Cup winner Lionel Messi and suspended Brazilian Neymar, but Kylian Mbappe, the Golden Boot winner in Qatar, received a rousing welcome from the Lens fans as he warmed up.
Lens were less welcoming once play started. They took the lead after five minutes when PSG goalkeeper Gianluigi Donnarumma blocked an effort from Massadio Haidara to Przemyslaw Frankowski who scored.
Hugo Ekitike replied three minutes later, swinging hard as Brice Samba dived to gather a cross and driving the ball through the Lens goalkeeper’s grasp.
Lens took control after 28 minutes. Seko Fofana won possession on the edge of his own box, drove through a couple of challenges then measured a pass between the PSG central defenders to Openda. The Belgium sprinted clear, and squeezed a shot under Donnarumma.
Lens struck the decisive blow two minutes into the second half.
Openda’s backheel in the penalty area left the defence flat-footed and set up Alexis Claude Maurice to score from close range.
The French league normally takes the holiday season off but with matches to make up following the World Cup, it played one round immediately after Christmas and another on Sunday and Monday.
They have dubbed the games ‘Celebration Week’, in English, as a nod to the English tradition of Boxing Day games, but many fans are suspicious or hostile.
Among protest banners unfurled by fans in an almost empty stand at Nantes, where the home team beat Auxerre 1-0, was one that complained that the league and broadcasters were “killing” them.
In Monaco, Aleksandr Golovin smashed in the only goal from outside the penalty area as the home team did just enough to beat Brest 1-0 and tighten their grip on fourth place.
Angers remain anchored to the bottom after suffering a ninth straight loss, falling 2-1 to visiting Lorient who broke their own run of six games without a victory.
The home team’s Moroccan World Cup stars Sofiane Boufal and Azzedine Ounahi, who have just returned from vacation and reportedly been promised lucrative transfers, were honoured before the match but did not appear.
“I was happy to see Sofiane and Azzedine,” said Angers coach Abdel Bouhazama. “For the moment they are here. For the rest, I leave that to the club directors. I take care of what happens on the pitch.”