The superstar grabbed a double on the night in the 2-2 draw in their Champions League clash as they came from behind twice.
Ronaldo bailed out Ole Gunnar Solskjaer once again and the result would have been great relief for the under-fire manager.
The night started off poorly as Atalanta took the lead thanks to a huge error by David De Gea in just the 12 minute.
Duvan Zapata was played in behind, with the striker keeping his cool and crossing for Josip Ilicic to hit a low, first-time strike.
The ball somehow squirmed underneath De Gea to give Ole Gunnar Solskjaer more problems.
Bailly had to produce a huge block to deny Zapata before United were forced into a first half change following an injury to Raphael Varane.
The formation shift had an almost instant impact with Mason Greenwood, Varane's replacement, having a hand in the equaliser.
An outstanding team move ended with Greenwood superbly playing in Bruno Fernandes, whose brilliant backheel teed-up Ronaldo to fire home just before the break.
It was Ronaldo's fourth consecutive Champions League goal for United since his return, the first player at the club to do so since Ruud van Nistelrooy in 2003.
talkSPORT's co-commentator Andy Townsend said: "Stunning, stunning goal. That is brilliant football from Manchester United. It is a special goal, it really is.
"Some clever little interplay and a stunning back heel from Bruno Fernandes. Cristiano Ronaldo was never going to miss."
United thought they had got a reprieve after Zapata had put the ball into the back of the net only for the assistant referee to raise his flag.
The forward skipped past Harry Maguire and turned the ball passed De Gea.
Tension inside the Gewiss Stadium turned to elation as the offside call was overturned by the VAR after a lengthy review.
Ronaldo got United out of jail again in stoppage time as the veteran forward struck a superb low effort past Juan Musso.
The goal proved to be a decisive one again for Ronaldo and United as it rescued a point that could be vital when it comes to knockout qualification.
The Portugal superstar has now scored late goals against both Villarreal and Atalanta (twice!).