The England international's current contract was due to expire at the end of next year, but he now will now prolong his stay by a further four years.
Rooney's future at United was the subject of intense scrutiny in the close-season, amid rumours the former Everton man had handed in a transfer request at Old Trafford and a public chase from Chelsea boss Jose Mourinho.
A delighted Rooney was relieved to finally end the months of rumour and speculation.
"I'm very happy to have signed a new long-term contract with Manchester United," said the United striker on his official website.
"This is one of the biggest clubs in the world and to know that I will be playing here for the majority of my career is something that I'm looking forward to.
"I'm happy that everything is now finalised and I can carry on concentrating on my football."
‘It was without a doubt one of the most important matches that I played in my career. It wasn’t just Champions League football – it was a whole club at stake’: Ex-Chelsea star opens up on key game which changed the Blues' fortunes forever
'I was Arsenal captain and really enjoyed it, but when Man City come calling, you have to listen': England international reveals reason for swapping London with Manchester
