Ibrahimovic then wrapped up the points on the half hour mark when he rose highest to guide home Ezequiel Lavezzi's right-wing corner via a deflection off a defender.
It was no more than the home team deserved as they ran a dispirited Benfica ragged throughout a very one-sided first period.
Laurent Blanc's charges inevitably dropped down a gear after the break but there was still an opportunity for Ibrahimovic to claim his treble - but he blazed over a rebound from eight yards out.
The result puts PSG clear at the summit of Group C with two emphatic wins from two outings.
5’ GOAL - Zlatan taps home at the far post after brilliant play down the right by Gregory Van der Wiel. The hosts carved Benfica wide open there.
25' GOAL - Marquinhos crashes home the rebound from close range after slick build up between Zlatan and Marco Verratti teed up Matuidi on the left of the area. The midfielder's driven cross was only parried by Artur, allowing Marquinhos to tap in.
30' GOAL - Ibrahmovic rises highest at the back post and heads home his second of the game via a deflection off a defender. More poor marking from a corner by the visitors.
71' MISS - Lucas makes an immediate impact, jinking his way towards goal and rasping in a shot that the keeper can only palm straight to Zlatan - who blazes over the top! A bad miss by the Swede from eight yards out.
74' CLOSE - Van der Wiel forces a smart save out of Artur from a tight angle with Cavani seeing his follow up well blocked on the line.
No Portuguese side has ever beaten PSG at the Parc des Princes in European competition. In seven matches there have been two draws and five defeats.
PSG are unbeaten in their last 10 Champions League games (7 wins, 3 draws), the longest current run. They have never failed to score during that sequence.
PSG are unbeaten at home in their last 25 games in European competition.
Benfica have won none of their last seven away games in the Champions League.
TALKING POINT - How good are PSG? Zlatan Ibrahimovic suggested in a pre-match interview that they were equipped to challenge for the Champions League crown this season. They certainly have the attacking talent at their disposal but the way they took their foot off the pedal in the second period will leave doubts for those who wonder if they can compete with the likes of Bayern Munich and Barcelona. But they did what was required of them against a toothless Benfica and they have maximum points from two matches in a group you would expect them to comfortably top.
MAN OF THE MATCH - Zlatan Ibrahimovic (PSG): The Swede hardly had to step out of first gear but grabbed two well-taken goals and gave the occasional cameo of his genius on a comfortable night for PSG.
PSG: Sirigu 6, Marquinhos 7, Alex 6, Maxwell 6, Van der Wiel 7, Motta 7, Matuidi 7, Verratti 7, Cavani 6, Ibrahimovic 8, Lavezzi 7. Subs: Lucas 7, Rabiot 6, Camara 6.
BENFICA: Artur 6, Luisao 6, Siqueira 6, Garay 6, Andre Almeida 6, Fejsa 5, Djuricic 5, Gaitan 6, Matic 6, Perez 5, Cardozo 5. Subs: Gomes 5, Markovic 6, Sulejmani 5.
THE MATCH IN A TWEET