The Serie A side confirmed the transfer had gone through in a statement on their official website. Their Twitter account posted a snap of the 26-year-old donning the iconic red and black jersey:
The move means Borini will depart Sunderland after two years, having joined the club on a permanent basis from Liverpool in 2015 a year after a successful loan spell.
Borini is the fifth signing made by Milan in a busy summer. Already the Italian giants have added Mateo Musacchio, Ricardo Rodriguez, Andre Silva and Franck Kessie to their squad for the 2016-17 season.
Of all the acquisitions made, the one of Borini is the most surprising, as the Italian has struggled to find his best form in the Premier League.
As we can see below, WhoScored.com do not rate the Italian forward highly:
Borini moved to Chelsea as a youngster before briefly returning to Italy, where he joined Parma before being immediately loaned to Roma. He impressed with the Giallorossi, and Liverpool moved to sign the striker in 2012.
At Anfield, Borini failed to show much, and in 2013-14 he was sent out on loan to Sunderland, where he helped the team avoid relegation with seven top-flight goals. However, after joining the Black Cats on a permanent deal in 2015, he only netted six times in the Premier League in two seasons.
Now he'll seek to kickstart his career in Milan. Matteo Bonetti of beIN Sports detailed where he thinks Borini will fit in:
With the Rossoneri, Borini will need to work hard and show a lot more class than he has in the last two seasons at Sunderland. Getting minutes ahead of the likes of Suso and Silva will be a big challenge for the ex-Liverpool man.
No longer a young player with potential, Borini is in what should be the peak years of his career. If it doesn't work out for him at Milan, it's a struggle to see quite where he goes from here.