Sunderland sign keeper Mannone from Arsenal
Mannone, 25, made only 23 appearances in eight years at Arsenal, although he started nine Premier League games last season and another four in the Champions League.
He links up with compatriot Paolo Di Canio, who took charge of Sunderland late last season and staved off the threat of relegation, the north-east club finishing one place and three points above the drop zone.
"The potential [of the club] is incredible," Mannone told Sunderland's website.
"I waited a long time for an opportunity like Sunderland, and for me it is a great one. I'm very excited. I am here to work hard and to show what I can do."
With Mignolet's departure, Mannone will compete for a first-team place with Ireland international Keiren Westwood.
Of his time at Arsenal, he added: "I had a great experience - it was a good learning curve for me.
"Even if I was probably a bit restricted in terms of opportunities. I learned a lot."