For the first hour at the Bernabeu, Kylian Mbappe produced an imperious performance as he scored one and had another two disallowed, leaving PSG 2-0 up on aggregate and seemingly in control of the tie.
But Benzema pulled one back before netting twice in a matter of seconds as PSG fell apart and the Spanish giants ruthlessly punished their ragged opponents to book a place in the last-eight draw.
Mbappe was fit to start for PSG after his injury scare earlier in the week, as Mauricio Pochettino was able to name his star-studded trio in attack.
It was Real who flew out of the blocks though, offering more in the opening minutes than they did in the entirety of the first leg. Marco Asensio found himself free in the box inside 40 seconds, only for his touch to let him down.
The threat from PSG was an obvious one, though that didn’t make it any less devastating. Dani Carvajal was run ragged in Paris and it was a similar tale at the Bernabeu, with the right-back having no answer to Mbappe. The Frenchman was played in and had a left-footed strike well saved by Thibaut Courtois.
A superb move from the visitors involving Neymar and Lionel Messi led to the Argentine dinking a ball over Courtois and across the face of goal, though fortunately for the home side it was a Real shirt that met it at the far post.
PSG thought they had the lead on the night when Nuno Mendes cut it back to Mbappe in the box and he drilled it low into the back of the net, but the offside flag was swiftly up to deny him.
The linesman saved Real once but not twice. Five minutes before the break, Neymar swept the ball over the top and Mbappe was once again charging free on the left. He opened up his body to set up the curling effort into the far corner, only to then whip it past Courtois at the near post and double PSG’s aggregate advantage.
Benzema had two good chances before the break, the first sent straight at Gianluigi Donnarumma and he then headed a big opportunity wide.
The Mbappe show continued in the second-half, as he produced an absolutely stunning dummy to sit Courtois down and then finish into an empty net, but once again the offside flag was up to rule it out.
From a magical moment to a calamitous one, as Donnarumma gifted Real a way back into the tie. The goalkeeper took an age on the ball, and under pressure then played it into the path of Vinicius Junior. He squared it into the box for Benzema who was free, and the Frenchman made no mistake from close range.
Vinicius should really have levelled the tie up with just under 15 minutes to go as a poor PSG clearance fell to him, but with only Donnarumma to beat he sent his shot well over the bar.
It was levelled up on aggregate shortly after though, as Luka Modric slid a glorious pass through to Benzema and with the help of a slight deflection he rifled it past the goalkeeper.
The celebrations were still in full flow when 12 seconds after kick-off, Benzema had the ball in the net and the PSG players looked around in complete astonishment as they fell apart in remarkable fashion.
The visitors gave it away straight from kick-off and Real burst forward with Vinicius, Marquinhos got his body in the way to seemingly get the situation under control but then bizarrely poked it straight into the path of Real’s main man. Benzema was only too happy to accept the gift, guiding the ball first time into the corner.
PSG never looked like getting the goal they needed to send it to extra-time, instead producing more shambolic defending as Real had further chances to extend the lead.
It’s another season without Champions League glory for PSG, the one trophy they truly crave, but 13-time winners Real marched on after a famous night.