He replaces Dutchman Louis van Van Gaal, who was dismissed on Monday, two days after the club’s FA Cup win.
“Jose is quite simply the best manager in the game today,” said United executive vice-chairman Ed Woodward.
He said he had always “felt an affinity with Old Trafford” and claimed he has “always enjoyed a rapport with the United fans”.
He added: “I’m looking forward to being their manager and enjoying their magnificent support in the coming years.
“There is a mystique and a romance about it which no other club can match.”bbc.