All eyes at the Luzhniki Stadium were on the Real Madrid star after his hat-trick in Portugal's opening game with Spain and, typically, he did not disappoint.
It took the captain only four minutes to make his mark in the way Morocco had feared, diving to get on the end of a Joao Moutinho cross and planting an unstoppable header into the net.
Ronaldo's goal put the European champions top of Group B before Spain play Iran at 19:00 BST on Wednesday, and extended his lead as the top scorer in Russia in the race for the Golden Boot.
Morocco, who last week failed in their bid to host the 2026 World Cup, became the first team to be eliminated from this one with one Group B game to go - but they did not go down without a fight.
Backed by thousands of noisy fans, who packed one end of the ground, they created enough chances to earn at least a draw - and would have got something out of the game with better finishing.
Too many of their shots flew wide, however, and the one time the North Africans did find the target with an effort of note, new Wolves keeper Rui Patricio produced a brilliant one-handed diving save to keep out Younes Belhanda's header.
The North African nation, beaten 1-0 by Iran in their opening game, are playing at the World Cup for the first time in 20 years.
Ronaldo again shows why Portugal rely on him
Ronaldo has been the undoubted star of the first week of this tournament and he ensured he will stay in the headlines with another decisive contribution.
He was the centre of attention from the moment his image flashed up on the huge screens, cheered by the Portugal fans and others who had travelled to Moscow solely to watch him - and jeered by the Morocco fans.
The 33-year-old's performance was not as spectacular as the one he produced about Spain, but he again showed why his team rely upon him so heavily.
Of Portugal's eight shots, he had six of them - including the one that mattered the most.
Ronaldo's other contributions, other than the flicked pass that released Goncalo Guedes to force a fine stop from Munir Mohamedi, were more fitful, but the intelligence of his movement and sheer presence up front meant he remained a threat.
There were no more magic moments, however, to the disappointment of the thousands in the crowd who recorded his two free-kicks from the edge of the area with their smartphones, only to see him smash them into Morocco's defensive wall.
Portugal offered little else in the way of a threat, and defensively the number of problems Morocco caused them must be a concern for their coach Fernando Santos, with bigger tests likely ahead.
But Ronaldo's Russian roadshow rolls into Saransk on Monday, and shows no sign of stopping.
Morocco out but not disgraced
Morocco now know they will be heading home after the group stage, but they will not depart in disgrace.
They gave their fervent support plenty to cheer in the Moscow sunshine and, just as in their opening defeat by Iran, can count themselves unlucky to leave left empty-handed.
The talk before the game was whether Herve Renard's side had a plan to stop Ronaldo and, while the former Cambridge United manager did not manage that, he did find a way to open up the Portugal defence.
Sadly for Morocco, they failed to capitalise when they found themselves in front of goal - of their 15 shots, four were on target, and only two truly tested Patricio.
The worst culprit was Mehdi Benatia, the Juventus defender who was tasked with tracking Ronaldo. He got forward too, but blasted wide when well placed and also missed the target with a header.
Morocco's defeat means African sides have lost five of their six games at this tournament, with Senegal's win over Poland the continent's only success so far.
Man of the match - Cristiano Ronaldo
'We have to earn more possession' - what they said
Portugal boss Fernando Santos: "It's a World Cup. This is a strong team, as were Morocco, but we have to grow.
"We did well defensively and we played well, but we need more than that. We have to change and earn more possession."
Morocco boss Herve Renard: "We qualified for a World Cup after 20 years and we've showed that we can play football."
Set-piece specialists - the stats
- After scoring 13 successive goals from open play at the World Cup, three of Portugal's four goals at 2018 have been from set-pieces.
- Morocco have lost seven of their past nine World Cup matches (W1 D1), failing to score in five of those games.
- Portugal have not lost against a non-European nation at a World Cup since June 2002, when they lost 1-0 to South Korea (W6 D3 since).
- Morocco have lost their opening two group games in three World Cups (also 1970 and 1994).
- Portugal have lost only one of their past 11 World Cup group games (4-0 v Germany in 2014), winning six and drawing the other four.
- Cristiano Ronaldo has scored Portugal's past five goals in World Cups, the first player to do so since Russia's Oleg Salenko in 1994.
- Portugal kept a clean sheet in a World Cup match for the first time since 2010, when they kept three in three group games - they had conceded in five consecutive games prior to this game.
Portugal will look to finish top of the group by beating Iran in Saransk on 25 June (19:00 BST), while Morocco face Spain in Kaliningrad at the same time.
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