The fee for Maguire eclipses the world record set by Virgil van Dijk’s £75m transfer from Southampton to Liverpool in January 2018.
The 26-year-old centre back, who will sign a five-year contract worth up to £200,000 a week with the option for a further 12 months, is set to have a medical on Saturday.
Maguire made it clear he wanted to leave and will have his United medical on Saturday
He will train with his new team-mates on Monday although it’s unclear if he will play in a behind-closed-doors game against Blackburn Rovers at Carrington on Sunday.
United have set up the match for any players who do not feature in the final pre-season fixture against AC Milan in Cardiff.
Maguire’s signing takes United’s summer spending to nearly £150m. They have focused on young British players, and he follows Dan James and Aaron Wan-Bissaka to Old Trafford.
Leicester, meanwhile, have made a healthy profit on a player who cost just £17m from Hull City two years ago.
Maguire has developed into one of England’s best centre backs in that time, and an established international under Gareth Southgate, but the fee will still be seen as excessive in some quarters even in the current market.
Manchester City dropped out of the bidding some time ago over Leicester’s demands for £85m plus £10m in add-ons, believing Maguire to be worth closer to £65m. United failed with two bids before offering the world record £80m deal that finally persuaded Leicester to sell.
The fee eclipses the previous world record £75m Liverpool splashed to sign Virgil van Dijk
Maguire was growing increasingly frustrated over his club’s stance, particularly because they rejected United’s advances for him last summer.
He signed a new five-year contract worth £80,000 a week at the King Power Stadium last September on the understanding that Leicester would allow him to leave if the right offer came in.
As negotiations with United reached deadlock this week, with the two clubs £15m apart, he missed training on Monday after phoning in sick and then pulled out of last night’s friendly with Atalanta because he was not in the right frame of mind to play.
United set a deadline of Monday to get the deal done so they would be able to switch to another target before the transfer window closes for Premier League clubs on Thursday.
Signing a new right back and centre back was seen as a priority after United finished last season with their worst defensive record in 40 years — and became even more important after Eric Bailly was ruled out until Christmas following knee surgery this week.
United had wanted to sign Maguire 12 months ago after a stunning World Cup with England
Manager Ole Gunnar Solskjaer will be delighted to have landed his top two targets Wan-Bissaka, £50m from Crystal Palace, and now Maguire.
It remains to be seen if the Sheffield-born player is worthy of replacing Van Dijk as the world’s most expensive defender, and can have as big an impact as the Dutchman who helped Liverpool win the Champions League in May. But this is a deal that will suit all three parties, ending a pursuit that started more than a year ago.
United will now focus on a deal to sell Romelu Lukaku to Juventus or Inter Milan, and sign a replacement before next week’s deadline.
They remain in talks with Juventus over a swap deal for Paulo Dybala that could also include Mario Mandzukic, who is more similar in style to Lukaku. However, Dybala is understood to have reservations over joining United and is demanding £350,000 a week to make the move.
The Argentine held talks with new Juve boss Maurizio Sarri and sporting director Fabio Paratici on Friday to decide his future, having been made aware that they are ready to let him go.
Inter could yet return with an improved offer for Lukaku, who was left out of the United squad who travelled to Cardiff for Saturday’s game against AC Milan, meaning he has missed all six pre-season friendlies.
Maguire’s former club Hull City are expected to earn 15 per cent of the profit made by Leicester for a player they sold for £15m two years ago.
Leicester have been linked with Brighton’s Lewis Dunk, James Tarkowski of Burnley and Watford’s Christian Kabasele.
MAGUIRE TO UNITED TIMELINE
JULY 2018: Manchester United express interest in Harry Maguire after his impressive World Cup campaign in Russia with England.
JULY 2018: Leicester rebuff United’s attempts to sign Maguire and open up contract talks with the defender to ward off interest.
JULY 2018: The then Leicester chairman Vichai Srivaddhanaprabha shakes hands with Maguire to allow him to leave the club the following summer should a big club come in for him.
SEPTEMBER 2018: Maguire puts pen-to-paper on a new five-year contract, worth £85,000-a-week.
JUNE 2019: United’s arch-rivals City enter the race to sign Maguire.
JUNE 2019: Reports suggest Maguire would prefer to join Premier League champions City over United.
JULY 2019: Leicester reject £70m bid from United for Maguire and ask for world-record fee.
JULY 2019: United consider other transfer options, including Napoli’s Kalidou Koulibaly
JULY 2019: City drop out of race after refusing to meet Leicester’s demands.
JULY 2019: Leicester boss Brendan Rodgers warns United he is under no pressure to sell Maguire and confirms club rejected two bids from his suitors.
AUGUST 2019: Maguire is left out of Leicester squad for their final pre-season friendly after calling in sick for training and holding talks with manager Brendan Rodgers because he is not in the right frame of mind.
AUGUST 2019: United agree world-record £85m fee with Leicester for Maguire.