Daley Blind has completed his £14m move to Manchester United as the Old Trafford club add to their summer spending spree.
The Dutch international has agreed a four-year contract after the clubs agreed a fee at the weekend leaving only a medical and personal terms to be completed.
The 24-year-old, who can play in defensive midfield or as a left-sided defender, will beef up a United backline that has so far looked vulnerable this season or add protection in central midfield.
Daley Blind told United's official website: "It is a real honour to sign for Manchester United.
"I have been at Ajax since I was seven years old and I will always have very fond memories of the club and of my time there.
"Louis van Gaal is a tremendously talented coach, I have worked with him at Ajax and also for the Netherlands national team and I cannot wait to work with him at the biggest club in the world."
Louis van Gaal said: "I am delighted Daley has signed for the club.
"He is a very intelligent and versatile footballer that can play in many positions.
"Daley is a great reader of the game, he has played under my philosophy over a number of years and he will be a great addition to the team."
Louis van Gaal earmarked Blind after working with him during his reign as Netherlands manager. He recorded the joint-top number of assists at the World Cup with three, including the diagonal ball for Robin van Persie's diving header in the 5-1 defeat of Spain.
Blind, who is the son of former Holland captain Danny Blind, has admitted having conversations with Van Gaal about where the 63-year-old wants to play him in either a 3-5-2 or 4-3-3 formation and said he toasted the deal with his girlfriend.