The attacking midfielder moves to Old Trafford for a British transfer record and says he cannot wait to link up with his new manager
The Argentine has penned a five-year deal with the Old Trafford club following four seasons at Real Madrid, culminating in a Champions League win last year.
He is excited to be moving to United, claiming that only they made leaving Carlo Ancelotti's side an appetising prospect.
"Louis van Gaal is a fantastic coach with a proven track record of success and I am impressed by the vision and determination everyone has to get this club back to the top – where it belongs," he told the club's official website.
"I now just cannot wait to get started."
The former Benfica man also explained that United were the only club for whom he would leave the Santiago Bernabeu.
"I am absolutely delighted to be joining Manchester United," he added.
"I have thoroughly enjoyed my time in Spain and there were a lot of clubs interested in me but United is the only club that I would have left Real Madrid for."
Di Maria will be available for the club's trip to Burnley on Saturday.