Konstantin Mikautadze was sent off and Simon Hickey amassed 27 points as Bordeaux Begles ended Montpellier's 100 per cent Top 14 record with an emphatic 47-17 rout, while Clermont Auvergne edged out Racing 92 on Saturday.
Montpellier arrived at Stade Chaban-Delmas with four wins out of four, but Raphael Ibanez's side ran riot to consign them to a first defeat of the season.
Bordeaux made it three home wins out of three in style, opening up a commanding 31-10 half-time advantage after Loann Goujon, Neville Edwards, Jean-Pascal Barraque and Apisai Naqalevu went over.
Timoci Nagusa scored his second try of the match to give the leaders hope early in the second half, but they were a man down for the last 15 minutes after giant lock Mikautadze was shown a red card for a forearm to the face of Matthieu Jalibert.
Hickey added another five-pointer for the home side late on, the fly-half converting every try and also landing four penalties in a magnificent performance.
Defending champions Clermont followed up their drubbing of Brive last weekend by beating Racing 23-21.
Alivereti Raka and Nick Abendanon claimed first-half tries for Franck Azema's men and Camille Lopez scored 13 points from the tee, with a Teddy Thomas score and a penalty try in vain for the 2016 champions.
La Rochelle moved up to second after a thumping 57-12 drubbing of Oyonnax, while Toulouse kept bottom side Brive waiting for a first win with a 22-19 away success and Pau triumphed 20-14 at Agen.