Perpignan overturned a 12-point deficit to defeat Castres 17-15 and move to the head of the Top 14 standings on Friday.
Romain Teulet kicked Castres into a shock 12-0 lead with four penalties before a long-range effort from Jerome Porical got the hosts on the board moments before half-time at the Stade Aime Giral.
Perpignan improved markedly after the interval and swiftly reduced their deficit to two points with a penalty try from steam-rollering forward pressure, converted by Porical, in the 47th minute.
Teulet, however, slotted another penalty to put Castres 15-10 clear entering the final 20 minutes and threatening the Catalans' long-standing home record.
But Guilhem Guirado fought his way through a maul for Perpignan's second try on 63 minutes to level the scores - and Porical duly converted to give the home side the lead for the first time, after which Castres, who has put in a huge effort in defence for the first hour, had nothing left in the tank.
Perpignan leapfrog Castres at the top of the table courtesy of the win.