Rennes had beaten PSG 2-1 on each of their last two visits to the Parc des Princes but, although the hosts were not clinical, Laurent Blanc's men ultimately strolled to victory.
The away side held their own early on and afforded PSG few sights of goal, but the champions' superior quality shone through just before the half-hour mark, as Lavezzi capped off a delightful move which involved Zlatan Ibrahimovic, Adrien Rabiot and Javier Pastore.
Rennes – who had not won any of their previous six in all competitions – went close to hitting back through Paul-Georges Ntep a few moments later, with Salvatore Sirigu called into action.
Edinson Cavani missed two opportunities to double PSG's lead at the beginning of the second half, and was jeered by sections of PSG fans when substituted.
The hosts failed to add to their lead in the latter stages, but regardless edged back to within a point of Lyon – who face Monaco on Sunday – and go into their Coupe de La Ligue semi-final at Lille on the back of five successive victories across all competitions.
Blanc seemingly had one eye on Wednesday's clash, as Blaise Matuidi and Marco Verratti were rested from the start, while Thiago Motta's absence through suspension left PSG struggling for fluency in midfield.
The hosts' patience eventually paid off, though, and they broke the deadlock in stylish fashion in the 29th minute.
Ibrahimovic carried the ball forward and combined with Pastore, who, after nudging it on to Rabiot, collected a chipped return pass inside the area and squared to Lavezzi for an easy finish at the end of a free-flowing move.
Rennes went close to restoring parity five minutes later, but Sirigu made a crucial save to deny Ntep after the forward pounced on Pastore's dreadful back-pass attempt.
PSG began the second period with renewed urgency and Cavani went close to adding his name to the score sheet twice in quick succession.
The Uruguayan first failed to connect with Marquinhos' teasing right-wing delivery, before seeing a controlled effort brilliantly tipped around the post by Benoit Costil following Lavezzi's defence-splitting pass.
Cavani then appeared to exchange words with Blanc upon his substitution in the 69th minute, as whistles rolled down from the stands, before Sirigu kept PSG ahead shortly after with an easy save to deny Christian Bruls.
Rennes enjoyed some pressure towards the end, but it ultimately proved to be too late as PSG claimed a routine victory, putting the pressure back on fellow title challengers Lyon and Marseille.
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