One of the worst-kept secrets within football finally became public knowledge when the Netherlands manager was named as the new boss of the struggling English giants.
United's record appearance holder Ryan Giggs will be his assistant after announcing he was ending his playing career.
Van Gaal, 62, has signed a three-year contract to succeed David Moyes who was sacked in April after a disastrous run of results culminating in failure to qualify for the Champions League.
A disciplinarian who has rarely lacked confidence in his own ability, Van Gaal has won domestic titles and cups with Ajax, AZ Alkmaar, Barcelona and Bayern Munich as well as guiding Ajax to Champions League glory.
And he was in no doubt he could enjoy more success in what will be his first job in English football.
"It was always a wish for me to work in the Premier League," explained Van Gaal.
"To work as a manager for United, the biggest club in the world, makes me very proud.
"I have managed in games at Old Trafford before and know what an incredible arena Old Trafford is and how passionate and knowledgeable the fans are.
"This club has big ambitions. I too have big ambitions. Together I'm sure we will make history."
However, his duties with the Dutch national side mean Van Gaal will not be able to join up with United until after the World Cup in Brazil, which would not be until mid-July if the Netherlands reach the latter stages of the tournament.
Giggs ‘thrilled’ with new challenge
Giggs, 40, who was in charge for the final four games of the season after Moyes's departure, said, "I am thrilled to have the chance to serve as assistant manager.
"Van Gaal is a world-class coach and I know I will learn a lot about coaching from being able to observe and contribute at such close quarters.
United executive vice-chairman Ed Woodward said the club had "secured the services of one of the outstanding managers in the game today.
"He has achieved many things in his career to date and Old Trafford provides him with a fitting stage on which to write new chapters in the United story."
Van Gaal quickly emerged as the favourite to take over at Old Trafford after Moyes was dismissed.
Moyes was the handpicked successor of former United manager Alex Ferguson after his compatriot retired as British football's most successful boss at the end of last season.
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