Five-time Ballon d'Or winner Ronaldo sealed a shock switch from Juventus to United on Tuesday, returning to the club where he spent six seasons earlier in his career.
The Portugal captain scored 118 goals in 292 appearances for United the first time around, helping the club to eight major honours during that successful period.
He remained prolific across nine years with Real Madrid and three with Juventus, scoring a combined 551 goals in 572 matches in all competitions.
Ronaldo is set to make his second United debut against Newcastle United on September 11th and Maguire cannot wait to link up with the superstar forward.
"It's amazing," Maguire said at a news conference on Wednesday while away on England duty. "Obviously I'm here at the moment so my focus on is on tomorrow's game.
"But for him to sign back for the club, for me the greatest player to play the game, it's amazing to have him and I'm sure he's going to have a huge impact on and off the field.
"Many players can look and learn and improve and then obviously it's going to improve our team as well with this goal scoring record, so it's amazing to have him in the club.
"I'm looking forward to meeting him in a few days."
Maguire is set to start England's World Cup qualifying clash with Hungary in Budapest on Thursday – the Three Lions' first match since losing the Euro 2020 final to Italy.
Gareth Southgate's men have won all three Group I matches so far but Maguire has warned his team-mates they must be ready for the showdown with second-placed Hungary.
"We need to be because it's going to be a tough test away to Hungary," he said. "If we're not ready mentally we won't perform our best and we won't get the result we need.
"The mentality of the squad will be tested and we need to overcome that and can show what we're about."
England are unbeaten in their past 13 matches against Hungary, winning 11 of those, since losing four in a row between 1953 and 1962 by an aggregate score of 17-5.
The Three Lions have only lost one of their past 50 matches in qualifying for the Euros and World Cup, meanwhile, going down 2-1 to the Czech Republic in October 2019.
Standout matches today