News the deal had been done came via the Red Devils' website, with the Manchester outfit paying a world-record fee for a defender to get the England international.
"I am delighted to have signed for this great club," said Maguire. "I have thoroughly enjoyed my time at Leicester and would like to thank everyone at the club, and the fans, for their fantastic support over the past two seasons. However, when Manchester United come knocking on your door, it is an incredible opportunity."
According to BBC Sport, Leicester will receive £80 million for the former Sheffield United and Hull City man. In the summer of 2017, the Foxes paid just £17 million to bring in the centre-back from the Tigers.
Maguire has made rapid progress in his two-year spell at the King Power Stadium. In his first season at the club, he established himself as a regular for Leicester, and by the end of the campaign, he was a regular for the England national team, too.
It was at the 2018 FIFA World Cup where Maguire became a household name. He was a crucial member of the three-man defence that helped England progress to the semi-finals of the competition and even scored the opening goal in the 2-0 win over Sweden in the quarter-finals.
Following his heroics in Russia, there were reports of United being interested in the player, with Leicester said to have then valued him at £70 million. Unsurprisingly, after another excellent season, they demanded more for his signature this summer.
What makes Maguire such a unique centre-back is his ability on the ball. WhoScored.com noted how capable he is bringing play out from the back:
Maguire also uses possession brilliantly, as he's adept at threading passes into midfield or switching play out to the flanks for his team-mates.
Crucially, he's a fine defender, too. Maguire is physical in the challenge and dominant when it comes to aerial battles, making him a difficult player to get the better of.
The challenge for Maguire will be coping with life at an elite side like United. While he's been able to take every test in his stride so far, there will be renewed expectations and added scrutiny on his game after making a move for such a huge transfer fee. It will be intriguing to see how he copes in these new circumstances.