The capital side went down 1-0 at Real Madrid on Tuesday but against lesser opposition they turned their chances into goals and now have 35 points from 13 games.
Angel Di Maria netted after six minutes. Ibrahimovic added two more goals while second-half substitute Lucas and Ezequiel Lavezzi also got on the scoresheet.
"We're doing something outstanding. I think we can finish the (league) season unbeaten," said Lucas.
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Olympique Lyonnais and St Etienne, second and third respectively on 22 points, meet on Sunday (2000 GMT).
Di Maria put PSG in front with a long-range effort that took a deflection in front of Toulouse keeper Al Ahamada.
Ibrahimovic headed home his 50th Ligue 1 goal at the Parc des Princes in the 18th minute after Marcel Tisserand headed the ball into the path of the Sweden striker.
Lucas came off the bench to replace Edinson Cavani and made an immediate impact, scoring with a header in the 66th minute.
He then slalomed through the defence and his shot was tipped away by Ahamada but Ibrahimovic poked the rebound into the empty net on 75 minutes, his ninth goal in his last eight league appearances.
Lavezzi rubbed salt into Toulouse's wounds three minutes later after he was left completely unmarked by the visiting defence.
"If we continue like this we will be able to rest some players after Christmas," said PSG centre back Thiago Silva.
(Reporting by Julien Pretot; Editing by Tony Jimenez)
