Ratcliffe has acquired a 25% stake in the club in a deal worth around £1.3 billion ($1.6bn) and will also take responsibility for football operations at United.
Manchester United have confirmed they have agreed to sell a minority stake to Sir Jim Ratcliffe, with the INEOS chairman also committed to investing another $300 million into the club.
Ratcliffe has acquired a 25% stake in the club in a deal worth around £1.3 billion ($1.6bn) and will also take responsibility for football operations at United.
A statement issued on Sunday said his further $300m commitment is "intended to enable future investment into Old Trafford."
"As a local boy and a lifelong supporter of the club, I am very pleased that we have been able to agree a deal with the Manchester United board that delegates us management responsibility of the football operations of the club," Ratcliffe said in the statement.
"Whilst the commercial success of the club has ensured there have always been available funds to win trophies at the highest level, this potential has not been fully unlocked in recent times.
"We will bring the global knowledge, expertise and talent from the wider INEOS Sport group to help drive further improvement at the club, while also providing funds intended to enable future investment into Old Trafford.
"We are here for the long term and recognise that a lot of challenges and hard work lie ahead, which we will approach with rigour, professionalism and passion. We are committed to working with everyone at the club -- the board, staff, players and fans -- to help drive the club forward.
"Our shared ambition is clear: we all want to see Manchester United back where we belong, at the very top of English, European and world football."
Ratcliffe will acquire 25% of the club's Class B shares, previously exclusively held by the Glazer family, and up to 25% Class A shares, which are traded on the New York Stock Exchange.