British billionaire Jim Ratcliffe said becoming a co-owner of Manchester United is a "great honour" and "responsibility" after his purchase of a minority stake was finalised on Tuesday.
The 71-year-old's investment, which will give him control of football operations at the 20-time English champions, was approved by the Premier League and English Football Association last week.
It was announced on December 24 last year that Ratcliffe had agreed to buy a 25 per cent stake in United from unpopular owners the Glazer family in a deal worth around GBP1.02 billion ($1.3 billion).
Following the completion of that deal, the founder of petrochemicals giant INEOS has invested a further $200 million to take his total stake to 27.7 percent and will inject $100 million more by the end of this year to enable investment in infrastructure at Old Trafford.
"This marks the completion of the transaction, but just the beginning of our journey to take Manchester United back to the top of English, European and world football, with world-class facilities for our fans," Ratcliffe said in a club statement.
"Work to achieve those objectives will accelerate from today."
United have not won the Premier League since former manager Alex Ferguson retired in 2013 and last won the Champions League in 2008 as their fortunes on the field have deteriorated during the Glazers' reign.
The Americans have been deeply unpopular with supporters ever since a leveraged takeover of the club in 2005 saddled the club with hundreds of millions of dollars of debt.
Joel Glazer, United's executive co-chairman, said: "I would like to welcome Sir Jim as co-owner and look forward to working closely with him and INEOS Sport to deliver a bright future for Manchester United."
A boyhood United fan, Ratcliffe has already met with leading supporters' groups and local politicians as he charts a course to lead United back to the top on and off the field.
Omar Berrada has been poached from local rivals and Premier League champions Manchester City to be the club's new CEO.
A pursuit of Newcastle's Dan Ashworth to be United's sporting director is also nearing completion as Ratcliffe aims to revolutionise the Red Devils' failing recruitment structure.
A UEFA report last week revealed that United had the most expensive squad in history at the end of last season with a combined transfer cost of $1.5 billion.
However, that investment has not reaped results on the field.
United crashed out of the Champions League group stages earlier this season and sit sixth in the Premier League.
The deal is just the latest of a portfolio of sports investments by Ratcliffe's INEOS, which has used its vast profits to fund a series of projects in football, cycling, Formula One, athletics and sailing.
