A defeat for Al Nassr and win for leaders Al Ittihad on Tuesday night would ensure the latter would be champions, something which seemed very possible when Ronaldo's side found themselves 2-0 down against Al Shabab after 40 minutes.
But a strike from Talisca just before the break halved the deficit before Al Nassr came out roaring in the second half.
Abdulrahman Ghareeb made it 2-2 on 51 minutes before Ronaldo's stunning effort turned the match around.
The Real Madrid and Manchester United legend rolled back the years as he received the ball midway through the Al Shabab half before turning inside and brilliantly curling it into the net from the edge of the box.
The Al Nassr fans in attendance celebrated wildly for their marquee player but it was the celebration the player he did which endeared him to them even more.
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Ronaldo did a Sujud, which is the act of low bowing or prostration to Allah facing the qiblah (direction of the Kabba at Mecca).
The 38-year-old then followed that up with his customary Siiuuu celebration.
The victory means Al Nassr are three points behind Al Ittihad with two league matches left.
A slip-up by Al Nassr at Ettifaq on Saturday means Al Ittihad will have the chance to seal their ninth Saudi Pro League crown.