Ronaldo’s compatriot Bruno Fernandes netted with a long-range rocket 10 minutes from full-time before Jesse Lingard bagged the fourth.
“This is what Cristiano is about. This was a day for everyone to enjoy,” United manager Ole Gunnar Solskjaer said.
This is what Cristiano is about. This was a day for everyone to enjoy
Ronaldo told BBC Sport: “I didn’t expect to score two goals. I expect one but not two. I have to appreciate the fans and what they did to me today. I feel so proud for that.”
A winner of three Premier League titles and one Champions League crown in six years with United before moving to Real Madrid, Ronaldo was making his first appearance for the club since 2009.
Thousands of fans gathered outside hours before kick-off to catch a glimpse of Ronaldo when he stepped off the United team bus.
Chants of “Viva Ronaldo” echoed around Old Trafford as supporters paraded in their idol’s famous number seven shirt.
Former United boss Alex Ferguson, whose phone call to Ronaldo played a key role in the Portugal striker choosing United over City, was watching from the stands.
Ronaldo’s name was cheered to the rafters before kick-off and inevitably he was destined to break Newcastle’s resistance two minutes into first half stoppage-time.
Mason Greenwood’s shot was spilled by Newcastle keeper Freddie Woodman and Ronaldo reacted quickest to finish from virtually on the goal-line.
Running to the corner to perform his trademark ‘Sii’ celebration, Ronaldo soaked up the acclaim from 76,000 ecstatic fans.
Ronaldo raises the roof
Newcastle threatened to spoil Ronaldo’s day when Manquillo equalised in the 56th minute with a fine finish from Allan Saint-Maximin’s pass.
But Ronaldo had other ideas and he restored United’s lead in the 62nd minute.
Luke Shaw’s through-ball sent Ronaldo racing clear on goal and he drilled a low shot under Woodman to raise the roof again.
Surfing the feel-good factor generated by Ronaldo, unbeaten United sit top of the table after a third win from their first four matches.
At the Emirates Stadium, Pierre-Emerick Aubameyang gave under-fire Arsenal manager Arteta some much-needed breathing space.
Gabon forward Aubameyang tapped home in the 66th minute, with a VAR check going in the Gunners’ favour as Norwich appealed in vain for offside.
After three successive defeats in the top-flight, Arsenal’s first league goal this season was enough to lift them off the bottom of the table and out of the relegation zone.
“I must say it has been the best 10 or 14 days in my professional career. Not the easiest, but the best. You learn a lot in difficult moments,” Arteta said.
Despite Ronaldo’s snub, Bernardo Silva showed Manchester City can cope just fine with their array of talent as he fired the champions to a 1-0 win at Leicester.
Portugal playmaker Silva struck in the 62nd minute with a close-range finish after Caglar Soyuncu blocked Joao Cancelo’s drive.
Chelsea striker Romelu Lukaku scored at Stamford Bridge for the first time as his double and a goal from Mateo Kovacic sealed a 3-0 win against Aston Villa.
After scoring on his second Chelsea debut in the win at Arsenal in August, Lukaku made it three goals from three appearances with predatory strikes in the 15th and 90th minutes.
Lukaku, who previously played for Chelsea from 2011 to 2014, is back with the Blues following his club record £98 million move from Inter Milan in the close-season.
Crystal Palace ended 10-man Tottenham’s perfect start to the Premier League season as Wilfried Zaha’s penalty and a late double from Odsonne Edouard sealed a 3-0 win.
Nuno Espirito Santo’s side had Japhet Tanganga sent off for two bookings in quick succession in the second half at Selhurst Park.
South Korea forward Hwang Hee-chan scored his first Premier League goal for Wolves in their 2-0 win at Watford.
Brighton won 1-0 at Brentford thanks to Leandro Trossard’s 90th-minute strike, while West Ham striker Michail Antonio was sent off in their 0-0 draw at Southampton.