Zlatan Ibrahimovic scored a second-half winning goal as Paris St Germain triumphed on a cold night in Nancy.
The Swedish striker was brought in by the wealthy capital club to provide the goals to carry PSG to success at home and in Europe.
Strikes such as his 74th-minute solo effort in difficult conditions at the Stade Marcel Picot show his worth to the cause. Today's goal was his 10th in 10 Ligue 1 outings since joining from AC Milan.
It lifted unbeaten PSG three points clear at the top of the Ligue 1 table, ahead of Toulouse, who won at home to Brest, and Marseille, who face a Sunday assignment against fourth-placed Lyon.
Nancy dominated the early stages, but they prop up the table with five points from a possible 30.
The hosts went close after just two minutes when Lossemy Karaboue played in Benjamin Moukandjo, who fired a right-footed shot that beat goalkeeper Salvatore Sirigu but struck the right post.
Another chance soon followed, as Karaboue freed Massadio Haidara on the left flank and he set off on a route towards goal, finishing his surge with a low shot that called for Sirigu to make a demanding save.
PSG threatened just before the half-hour mark when Jeremy Menez tore forward and crossed for Mamadou Sakho, whose header found the target but also the hands of a diving Guy N'Dy Assembe.
The goalkeeper produced a second fine save in quick succession when a free-kick from Ibrahimovic was deflected to Kevin Gameiro and his follow-up shot threatened the home net.
Menez curled a shot inches wide of the left post in the 48th minute, before Nancy threatened for the first time in a while. A positive counter-attack concluded with Thomas Mangani's left-footed shot being blocked by Sirigu.
Mathieu Bodmer came to PSG's rescue soon before the goal arrived when he headed away a shot from Yohan Mollo that had beaten Sirigu.
Blaise Matuidi then fed Ibrahimovic the ball in midfield.
He darted to the right, riding his luck as well as several challenges, before lashing a left-footed shot inside the right post from 20 yards.
N'Dy Assembe thwarted Menez in stoppage-time with a solid save from the winger's powerful strike.