The Netherlands international has penned a four-year deal with the 20-time English champions after United agreed a £14m deal with Eredivisie champions Ajax.
And Van Gaal, who helped Blind thrive at the World Cup in Brazil, is thrilled to sign the versatile defender on deadline day of the summer transfer window.
“I am delighted Daley has signed for the club,” Van Gaal told United’s website.
“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.”
Blind added: “”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.”
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