Mount has signed a five-year contract with the option for a further year.

"Having met with the manager, and discussed his plans, I couldn't be more excited for the seasons ahead," said England international Mount.

"Everyone can see that the club has made big steps forward under Erik ten Hag. I am hugely ambitious; I know how amazing it feels to win major trophies and what it takes to do it. I will be giving everything to experience that again at Manchester United."

Chelsea rejected United's first three bids for Mount before an agreement was reached. The London club spent £600m last season and needed to sell to ease Financial Fair Play (FFP) concerns.

They preferred not to lose a player who joined them aged six, but were unable to negotiate a new contract with his deal set to expire next year.

"It's never easy leaving the club where you grew up, but Manchester United will provide an exciting new challenge for the next phase of my career," Mount added.

"Having competed against them, I know just how strong a squad it is that I'm joining, and I can't wait to be part of this group's drive to win major trophies."

Mount, who has scored 33 goals in 195 appearances for Chelsea since making his senior debut in 2019, missed the end of the domestic season with injury as the Blues came 12th - their lowest finish for more than 25 years.

The player will wear the number seven shirt at Old Trafford, as worn by Cristiano Ronaldo and, before him, David Beckham. The number was offered to Mount by Ten Hag during their discussions, to show the player how much he was wanted.

Mount 'a perfect fit for this squad'

Mason Mount: Watch Chelsea midfielder's FA Cup goal against Man Utd

Ten Hag's side finished third in the Premier League and while the Dutchman has prioritised a new striker this summer, Mount's ability to operate in advanced positions is understood to have made him an attractive option for the club.

Manchester United football director John Murtough said: "Mason is an extremely intelligent footballer and has so many fantastic technical qualities that will significantly add to our squad.

"We have admired his talents for a long time, so we are delighted that he has chosen to take the next steps in his career here at Old Trafford.

"His style of play and attributes are a perfect fit for this squad, and we all believe that he will only improve further working with Erik ten Hag and his coaching staff."

Mount won the Champions League in 2021 with Chelsea and started during the side's 1-0 win over Manchester City in the final. He also won the Fifa Club World Cup and Uefa Super Cup with the Blues.

He has been capped 36 times by England, scoring five goals, and was part of Gareth Southgate's squad for the 2022 World Cup in Qatar.

Mount came through Chelsea's academy before joining Vitesse on loan for the 2017-18 season, scoring nine goals in 29 Eredivisie appearances.

The following campaign he was loaned to Derby County, scoring eight goals 35 Championship games under manager Frank Lampard as the Rams suffered a 2-1 defeat by Aston Villa in the play-off final.

Upon his return to Chelsea in 2019, Mount made his breakthrough under the newly appointed Lampard and became a key player at Stamford Bridge.