Paris Saint-Germain slipped to a first defeat of the season as second-placed Lens demonstrated their Ligue 1 title credentials with an impressive 3-1 victory at Stade Bollaert-Delelis.
Goals for Przemyslaw Frankowski, Lois Openda and Alexis Claude-Maurice in an entertaining New Year's Day contest reduced PSG's lead at the summit to four points.
Hugo Ekitike equalised in the first half, but Christophe Galtier's side were second best in their first game of 2023 as they await the return of Lionel Messi following his World Cup triumph with Argentina.
It was a dream start to 2023 for Lens boss Franck Haise, who celebrated his 100th match in charge in style.
A raucous crowd did not have to wait long for fireworks, with Frankowski on hand to apply the finish after Gianluigi Donnarumma could only parry Massadio Haïdara’s strike into his path five minutes in.
PSG promptly struck back three minutes later, when Ekitike poked a finish beyond Brice Samba, though the Lens keeper claimed the ball was kicked out of his hands by the forward.
Lens took that setback in their stride, and they were back in front with a goal on the break just before the half-hour mark, Openda taking a pass from captain Seko Fofana and beating Marquinhos before firing under Donnarumma.
Things went from bad to worse for PSG when Openda turned provider with a superb backheel for Claude-Maurice to rifle home two minutes after the restart.
There was no way back for the Parisian giants as Lens showed they are capable of putting up a serious title fight.
What does it mean? PSG lose unbeaten record
PSG knew a win would have given them a commanding 10-point lead, but Lens were magnificent in the battle of the top two to show they mean business.
Defeat not only trims the gap but brings to an end the champions' 12-game unbeaten run away from home in the French top flight.
Mbappe kept quiet in Verratti's 400th game
After winning the Golden Boot in Qatar and scoring a late winner on his return to club duty against Strasbourg, Kylian Mbappe was unable to produce more heroics.
The France attacker had two shots on target and failed to find the back of the net on a night in which team-mate Marco Verratti suffered a defeat in his 400th appearance for the club.
Lens apply the heat
This was a major statement from Lens, who have only been beaten once in Ligue 1 this season and were good value for a huge victory.
They have now recorded nine straight home wins in the league, matching their previous best such streak set between March and September 1985.
Key Opta facts
- PSG's loss was their first in Ligue 1 since going down 3-0 to Monaco on March 20 last year, ending a run of 25 games without defeat in the top flight.
- Openda scored his eighth goal in Ligue 1 this season, the highest tally for a Belgian player in the top five European leagues in the current campaign. He also provided his first assist.
- Haise has four of his five games in charge of Lens against Ligue 1 champions - that 80 per cent record being the highest of any coach in the 21st century to have won at least three such matches.
- Sergio Ramos suffered his first loss as a PSG player in his 35th appearance with the club in all competitions (W27 D7). His previous defeat came in May 2021 for Real Madrid against Chelsea in the Champions League.
Lens will face Linas-Montlhery in the Coupe de France on Saturday, while PSG will travel to Chateauroux in the same competition a day before.