Moscow’s Luzhniki Stadium was the venue for a game that saw both sides looking for their first win following Morocco’s 1-0 defeat to Iran and Portugal’s 3-3 draw with Spain.
Before the match Portugal coach Fernando Santos said his team must not solely rely on their captain but, once again, it was their superstar who proved to be the match winner.
Ronaldo followed up his hat-trick against Spain with a fourth-minute diving header which was his 85th goal for his country in 152 games.
No other European player has scored as many as the maestro and only Ali Daei, with 109 goals for Iran, is above him in the scoring charts.
Morocco can count themselves unlucky not to have taken at least a point as they chased and harried a hesitant Portuguese defence in which Raphael Guerreiro was given the run-around by Watford’s Nordin Amrabat.
In midfield William Carvalho lacked authority and was well off the pace whilst Ronaldo was given little support as he ploughed a lone furrow up front.
Yet despite their failings Portugal managed to hang on thanks to some abysmal finishing by the Morocco front men. Twice they went close before the hour mark through Younes Belhanda, the second effort a bullet header was brilliantly saved by Rui Patrício as he threw himself full length to his right to claw the ball away to safety.
The 1-0 victory puts Portugal, with four points from two games, in a strong position to progress from Group B while Morocco become the first team to be eliminated from the tournament after a second defeat in as many games.
Portugal play their final group game on Monday evening against Iran.