The 'Special One' joins the Red Devils with an option to stay on until at least 2020.
The stage is set for the marriage of two of the biggest names in football: Jose Mourinho, the manager who collects trophies wherever he goes, and Manchester United, England's most successful club and a global giant.
Mourinho joined the Red Devils on a three-year contract with an option to stay on until 2020 and will reportedly be earning a salary worth more than $20 million a year.
The Portuguese 'supercoach' was announced on Friday after a legal hiccup with his name and image rights tied to his former club Chelsea.
For many Chelsea fans, Mourinho is 'forever their man', but according to the 53-year-old's own admission, 'it was time to write another story'.
Mourinho, sacked by Chelsea in December, had been widely expected to succeed Van Gaal. His agent Jorge Mendes met with Manchester United officials on Tuesday to discuss personal terms.
Mourinho said, "To become Manchester United manager is a special honour in the game. It is a club known and admired throughout the world. There is a mystique and a romance about it which no other club can match.
Mourinho at Man U for three years is scary. He brings the swag back to Old Trafford.— Chris Banchero (@ChrisBanchero) May 27, 2016
"I have always felt an affinity with Old Trafford; it has hosted some important memories for me in my career and I have always enjoyed a rapport with the United fans. I'm looking forward to being their manager and enjoying their magnificent support in the coming years."
In two spells at Chelsea, the Portuguese won the Premier League three times, including their first league title in 50 years, and both the FA Cup and League Cup.
He also won league championships in his first seasons at Porto and Inter Milan before helping Real Madrid to their first La Liga crown in four years.
The 'Special One' as he is widely known, is no stranger to controversy and doesn't shy away from speaking his mind.
Below are some of his most remembered quotes:
I have top players and I'm sorry, we have a top manager. Please do not call me arrogant because what I say is true. I'm European champion. I'm not one out of the bottle. I think I'm a special one.
-In his introductory Chelsea press conference in 2004
Young players are like melons. Only when you open and taste the melon are you 100% sure that the melon is good.
-On bringing through young players up Chelsea's ranks.
I think he is one of these people who is a voyeur. He likes to watch other people. There are some guys who, when they are at home, have a big telescope to see what happens in other families. He speaks, speaks, speaks about Chelsea.
-On Arsenal manager Arsene Wenger, who criticised Chelsea's transfer policy.
"Omelettes, eggs. No eggs, no omelettes. And it depends on the quality of the eggs in the supermarket. They are class one, two or three and some are more expensive than others and some give you better omelettes. When the class one eggs are not available, you have a problem."
-On transfer dealings
"The only club where her husband replaced me was at Inter Milan, where in six months he destroyed the best team in Europe at the time. And for her also to think about me and to speak about me, I think the lady needs to occupy her time, and if she takes care of her husband's diet she will have less time to speak about me. "
-To Rafael Benitez's wife who says her husband always cleans up Mourinho's messes.