PSG, boasting expensive new signings Ibrahimovic and Ezequiel Lavezzi and expected to coast to the title this term, came back down to earth with a bump after five minutes when defender Maxwell diverted a left-wing cross into his own net.
Lorient have long been the capital club's bogey side and a shocked Parc des Princes could hardly believe their eyes when Jeremy Aliadiere ghosted through the entire PSG defence after a quick break to easily score a second on the stroke of halftime.
Former AC Milan striker Ibrahimovic pulled one back midway through the second half with a trademark goal of strength and flair and then netted a penalty late on to spare some of coach Carlo Ancelotti's blushes.
Reigning champions Montpellier, who stunned Ligue 1 by beating PSG to the title last term, drew 1-1 with Toulouse in the opening game of the season on Friday while Girondins Bordeaux were 3-2 winners at Evian on Saturday.
- Ezequiel Lavezzi