Sir Jim Ratcliffe has said it will take “time and patience” to “bring sporting success” back to Manchester United.
The British billionaire has agreed to buy a 25% stake in the Old Trafford club for about $1.3bn (£1.03bn).
His Ineos Group will take control of football operations and Ratcliffe will also provide $300m (£236m) for future investment into United’s stadium.
Ratcliffe has told supporters “we recognise our responsibility as custodians of the club on your behalf”.
In an open letter to fans, he added:
“I believe we can bring sporting success on the pitch to complement the undoubted commercial success that the club has enjoyed.
“It will require time and patience alongside rigour and the highest level of professional management.
“You are ambitious for Manchester United and so are we. There are no guarantees in sport, and change can inevitably take time but we are in it for the long term and together we want to help take Manchester United back to where the club belongs, at the very top of English, European and world football.
“I take that responsibility very seriously.”