Montpellier bounced back from their European Cup quarter-final exit last week to edge Toulouse 10-8 and boost their French Top 14 play-off hopes on Saturday.
Defending champions Toulouse could have snatched a share of the points in the last minute after young centre Gael Fickou had scored his side's only try.
But Lionel Beauxis, who endured a miserable day with the boot, failed with the conversion, his fourth miss in five attempts.
The result left Toulouse in third place, six points behind Clermont with two games of the regular season left.
Montpellier, knocked out of Europe by Clermont, moved into fifth spot, four points ahead of Racing Metro and just one behind Castres.
Winger Timoci Nagusa had scored a brilliant individual try for Montpellier after 48 minutes.
The Fijian shrugged off two tackles before sprinting 40 metres to score his seventh try of the season.
Meanwhile, eastern-French side Oyonnax were promoted to the top flight for the first time in their 104-year history after taking the second division title.
They secured their place in the Top 14 despite losing 30-29 to Brive.
The town of Oyonnax has a population of just 23,000.
The club has a 20-point lead over closest rivals La Rochelle with only four games left.