The Ligue 1 champions were second best for much of the first half and trailed to Raphael Guerreiro's 42nd-minute strike at the break on Saturday.
But PSG emerged a new team in the second half and Javier Pastore unlocked Lorient's defence for Edinson Cavani to score the equaliser on the hour-mark.
And Jean-Christophe Bahebeck completed the comeback just eight minutes later, combining with Marco Verratti for the winner.
PSG are just one point adrift of Marseille, who are scheduled to play Lens on Sunday.
Lyon are just a point behind PSG after rallying late to beat Nice 3-1 on the road.
Gregoire Puel put the hosts ahead just six minutes after the break but that is as good as it got for Nice.
Steed Malbranque equalised for Lyon in the 64th minute before Alexandre Lacazette scored twice in the final 10 minutes to secure victory.
Guingamp climbed out of the relegation zone with a 1-0 win over Bastia.
The hosts recovered from last weekend's 7-2 thrashing at the hands of Nice with an important home success to lift them off the bottom and up to 16th.
Guingamp got some help along the way, however, as it was actually Bastia defender Guillaume Gillet, who scored the vital goal in the 32nd, putting the ball through his own net.
Lille drew 1-1 at home to fourth-placed Saint-Etienne without coach Rene Girard as he served the first of his four-match ban from match-day duties for being sent to the stands for the second time this season.
Veteran Florent Malouda converted a 90th-minute penalty as Metz, who squandered a two-goal lead, prevailed 3-2 against 10-man Caen.
Meanwhile, goals from Kevin Berigaud and Anthony Mounier inspired Montpellier to a 2-0 victory against cellar-dwelling Evian.