Ronaldo had scored twice -- including his 100th goal for Real in the competition -- as they won 3-1 in the first leg in Spain last month, and his header early in the second half at the Parc des Princes effectively ended the French club's hopes of progressing.
Edinson Cavani equalized on the night for PSG, but only after they had Marco Verratti sent off, and Casemiro's late goal secured an ultimately comprehensive 5-2 aggregate victory for Zinedine Zidane's side.
PSG never looked like turning the tie around in the absence of the injured Neymar, and it was a horribly flat way for them to exit the competition.
As they limp out, Real's dream of becoming the first team in more than 40 years to win three successive European Cups remains alive.
A year after their spectacular collapse against Barcelona in the last 16, when they were humiliated 6-1 away in the return after a stunning 4-0 win at home, PSG had hoped to produce a memorable comeback themselves this time.
Yet, shorn of the world's most expensive player, who is back in Brazil recuperating from a foot operation, they struggled to create chances, and the night will be remembered just as much for the stupidity of a section of their supporters.
Flares were lit en masse on several occasions at one end of the ground, once even leading to a brief stoppage in play, and PSG will face punishment from UEFA as a result.
Di Maria flops
Without Neymar, this was Angel Di Maria's big chance to shine after he was left on the bench for the entirety of the first leg, but nothing came off for the Argentine against his former side, his performance symbolic of a wider malaise in the home ranks.
They had only made Real goalkeeper Keylor Navas work once in the first half, from Kylian Mbappe's shot in the 43rd minute.
In contrast, Alphonse Areola had kept the home side in the game with two fine saves to deny Sergio Ramos and Karim Benzema before the interval.
That just delayed the inevitable. Having come close with a header moments earlier, Ronaldo broke the deadlock in the 51st minute, heading in a Lucas Vazquez cross for his third goal in the tie.
The goal had come from an error by Dani Alves initially, and it completely punctured PSG and the atmosphere.
The tie had escaped them before Verratti was sent off midway through the second half, picking up a second yellow card for dissent.
Substitute Javier Pastore's header deflected into the net off Cavani in the 71st minute to level the scores on the night, but more poor defending allowed Real to make it 2-1 with 10 minutes left.
Unable to clear their lines in their own area, PSG saw Casemiro's shot go in via a Marquinhos deflection.
With Marco Asensio and Isco both hitting the post in the second half for Real, the visitors more than deserved their win on the night, as well as in the tie.
That rubbed more salt into the wounds for PSG, who had not lost any of their previous 51 home games in all competitions, a run going back two years to before the start of Unai Emery's reign as coach.
This defeat is likely to hasten the end of his time in charge.