The reigning Serie A champions confirmed Ribalta's departure earlier on Friday (23 June), stating that he will be leaving in order to "take on a new professional adventure elsewhere".
"It has been a wonderful few years here," he said. "My thanks go to all involved with the club, particularly [general manager] Giuseppe Marotta and [sporting director] Fabio Paratici for the faith they have shown in me since day one.
"I will look back on my time at Juventus with great pleasure."
Ribalta now heads to Old Trafford, where he is expected to work in tandem with chief scout Jim Lawlor and head of global scouting Marcel Bout.
Respected Italian journalist Gianluca Di Marzio claims that the Spaniard will have a "significant role in picking players" and act as a point of reference for scouting and recruiting.
United have significantly revamped their scouting and academy set-up over the past year or so, reportedly making more than 50 new appointments since Mourinho succeeded Louis van Gaal in May 2016.
The likes of Sandro Orlandelli, Tommy Moller Nielsen, Roy Beukenkamp, Gerardo Guzman and Armand Banneker have all been taken on, while David Harrison and Lyndon Tomlinson were both poached from local rivals Manchester City last year and began work in January.
United have already made one first-team signing so far this summer, with long-term target Victor Lindelof arriving from Benfica in a deal worth approximately £31m ($39.4m). They are believed to be close to wrapping up a deal for Real Madrid striker Alvaro Morata, whom Ribalta is said to have played a crucial part in signing for Juventus back in 2014. This latest addition will presumably only aid that particular pursuit.
Ribalta is additionally rumoured to have been influential in bringing Paul Pogba to Juve following his initial departure from United back in 2012. He is also credited with playing a key role in the signings of several other prominent Bianconeri players past and present including the likes of Dani Alves, Kingsley Coman, Alex Sandro and Paulo Dybala.