Ederson is set to sign a four-year deal with the Red Devils with an option to extend his stay for an additional 12 months in a move that has been reported for a number of months.
The 26-year-old will step in for veteran Brazilian Casemiro, who will depart this summer after several years at the club following an emotional goodbye at Old Trafford at the end of the campaign.
He is set to become the first signing of the Michael Carrick era as transfer guru Fabrizio Romano revealed the deal is set to be announced soon.
"Manchester United formally closed their first signing of the summer. Was a 'here we go' a few days ago, but now everything is in paper between Manchester United and Atalanta for Ederson. The Brazilian midfielder is a Man United player from today," Romano reported.
"What's needed now is Ederson, after the holidays, go to England, take his official medical, sign the contract. I'm told that a first unofficial medical already took place with the authorisation of Atalanta.
"Everything is okay between Ederson and Man United since months ago. He only wants to go to Man United, and now also the agreement closed between the two clubs on paper."
Ederson was named in Brazil's 55-man expanded World Cup squad but missed out on manager Carlo Ancelotti's final selection. He will have a much-needed rest this summer, making his move to Old Trafford easier as he stays in Europe.