Once mighty Olympique Lyon triumphed in the big derby at Saint Etienne 4-1, with former Les Verts forward Bafetimbi Gomis scoring for the visitors as they leapfrogged their rivals and moved up to joint third with exactly the same record as PSG.
St Etienne went ahead through Carlos Bocanegra but Gomis lashed an equaliser through a crowd of bodies before a Cris header from a corner was deflected into his own goal by Moustapha Bayal Sall.
Cris's fellow Brazilian Michel Bastos and Jimmy Briand sealed the win in the second half of a heated end-to-end encounter.
France striker Gignac, who said this week he had given up money from his image rights at last year's World Cup after Les Blues' poor showing, struck for Didier Deschamps' Marseille in the 45th and 70th minutes.
"It was complicated, it's never easy to take three points at Sochaux as they are good at home," Deschamps told reporters.
PSG were second going into the game at the Parc des Princes but could not break through with Claude Makelele's long shot saved and Guillaume Hoarau's diving header hitting the post.
Monaco boosted their hopes of avoiding a shock relegation with a 3-1 win over FC Lorient in the principality while Girondins Bordeaux's mid-table malaise continued with a 2-1 home defeat by Caen which puts pressure back on coach Jean Tigana.
AC Arles-Avignon, well adrift at the bottom, drew 0-0 at home to Montpellier and mid-table AS Nancy beat Auxerre 3-1.
