The Cameroonian goalkeeper has kept 104 clean sheets in 255 club appearances.
Andre Onana said:
“To join Manchester United is an incredible honour and I have worked hard all my life to get to this moment, overcoming many obstacles along the way. Walking out at Old Trafford to defend our goal and contribute to the team will be another amazing experience. This is the start of a new journey for me, with new teammates, and new ambitions to fight for.
“Manchester United has a long history of incredible goalkeepers, and I will now give everything to create my own legacy in the coming years. I am excited by the opportunity to work again with Erik ten Hag, and I can’t wait to play my part in the success I know he is determined to deliver at this great football club.”
He won three league titles and two KNVB Cups with Ajax before joining Inter in 2022.