Ronaldo came up with the 81st minute winner for the Red Devils who trailed 2-0 at half-time after goals from Mario Pasalic and Merih Demiral.
Marcus Rashford pulled one back in the 53rd minute, before Harry Maguire lashed home at the back post for a 75th minute equalizer.
But United’s Portuguese superstar Ronaldo came up with the winner to send Old Trafford into a frenzy amid growing pressure on Solskjaer.
“He’s great in front of goal,” Solskjaer told reporters after the game.
“If anyone wants to criticise him for work-rate or attitude, just watch this game. Watch how he runs around.
“The header is not on a par with his Roma one but hes still got a leap and timing like no-one else.”
Villarreal triumphed 4-1 in the other group game against Young Boys, meaning United are top with six points, ahead of Atalanta and Spaniards both on four.
In Group H, Chelsea outclassed Malmo 4-0 with Jorginho netting twice from the spot, while Juventus found a late winner to triumph 1-0 at Zenit St Petersburg.
In Group G, Sevilla had a third straight draw finishing 0-0 at Lille, while Salzburg] got past Wolfsburg 3-1 with starlet Karim Adeyemi netting early.