Borini joined Liverpool from Parma in 2012 but struggled to break into the first team and subsequently spent last season on loan at the Stadium of Light.
The 23-year-old striker impressed Black Cats manager Gus Poyet during his stint in the North East - scoring 7 goals in 32 league appearances - and the Uruguayan has since been working on a deal to sign the Liverpool man on a permanent deal.
Borini was reportedly at the top of Poyet's shopping list and, after having an initial bid of £10 million turned down by the Anfield club, a fee of £14m was agreed on Friday.
The Italian will become the second striker to depart Liverpool following Luis Suarez's transfer to Barcelona.
- Sports & Recreation
- Gus Poyet