With Ederson set to remain as Manchester City's first-choice keeper for the foreseeable future, having arrived at the Eithad for an extortionate amount of money, Gunn will look to lay his claim for a starting berth elsewhere.
After narrowly avoiding relegation from the Premier League last season, Saints have bolstered their squad with the addition of Stuart Armstrong and Mohamed Elyounoussi.
Gunn, who joined the Blues in 2011, never played first-team football for City, despite being on the bench several times.
The 6ft 5in stopper spent last season back with Norwich in an impressive loan spell, and he even earned a call-up to the England squad back in November as he starred at Carrow Road.
Southampton split goalkeeping duties between Fraser Forster and Alex McCarthy last term.
Good business from Southampton getting Angus Gunn in.