Man United revealed they had reached an agreement with Torino over the transfer of the Italian on Saturday.
He joins on a four-year deal with the option of extending for a further year.
Van Gaal praised the 25-year-old’s versatility and revealed he will join up with the rest of the squad in the next few days.
“Matteo is a right-sided full back with the versatility of also being able to play on the left. He is a strong defender and has the ability to go forward in the attacking positions which is a fantastic attribute to have and much needed in the fast rhythm of the Premier League,” he said.
“Matteo will be a great addition to the team. I am delighted to welcome Matteo to the club and look forward to working with him in the coming days.”
Van Gaal is fond of a versatile player and Darmian certainly falls into that category. Antonio Valencia put in a number of poor performances last term and Darmian represents a huge upgrade on him.
United also confirmed they are set to sign Bastian Schweinsteiger on Saturday and it is exciting to see the club seal transfers. Southampton midfielder Morgan Schneiderlin has also been strongly linked with a move to Old Trafford and there is a real possibility that there could be developments with his situation in the next 24 hours.