United will pay an initial £34.7m for the 23-year-old, who has penned a five-year contract with the option of a further 12 months to become Ole Gunnar Solskjaer's first recruit ahead of the 2020-21 season.

Van de Beek was one of the star performers for Ajax as it embarked upon a memorable run to the semi-finals of the 2018-2019 Champions League.

However, he now follows former team-mates Frenkie de Jong, Matthijs de Ligt and Hakim Ziyech in making a big-money move away from the Johan Cruijff ArenA, having sat out Ajax's weekend friendly against Eintracht Frankfurt.

"I cannot begin to explain how incredible an opportunity it is to join a club with such an amazing history," he told United's website.

"I would like to thank everyone at Ajax. I grew up there and I will always have a special bond with the club.

"I am now ready to take the next step in my career and perform at the highest level and there is no higher standard than Manchester United.

"Everyone has told me how amazing the Old Trafford atmosphere is and I am looking forward to experiencing that, once it is safe for the fans to return.

"This team has some of the best midfielders in the world and I know that I can learn from them and also bring my own strengths to the group.

"Having spoken to the manager about his vision for this team, the direction that the club is going in is hugely exciting and I cannot wait to be a part of that."

Van de Beek played 175 times for Ajax's first team after progressing through the club's feted youth categories, scoring 41 times.

He must now look to establish himself in a talent-stacked United midfield alongside Bruno Fernandes and Paul Pogba.

"Donny has all of the technical attributes needed to perform in this team and has the personality required to succeed at Manchester United," Solskjaer said.

"His ability to see space, time his movements and read the game will really complement the qualities that we have in midfield and his arrival really strengthens the depth of talent we have in that position.

"Donny's performances in the Eredivisie and in Europe have been excellent over the last few years and we are all looking forward to working with him."

United starts its Premier League campaign at home to Crystal Palace on 20 September (AEST) – a week later than the majority of its top-flight counterparts, having been involved in the latter stages of the Europa League.