The 24 year old exits the Black Cats having helped them to win promotion to the Premier League with 47 Championship appearances during the 2024/25 season.
Neil fell down the pecking order at Sunderland last campaign and after just three league appearances, he moved on loan to second tier Ipswich Town.
At Portman Road, Sunderland academy graduate Neil played 16 times as the Tractor Boys also secured promotion to the Premier League with a second-place finish.
Sky Sports report that Saints are in talks with Neil over a free transfer to St Mary’s and are close to signing him, with the midfielder high on head coach Tonda Eckert’s wish list.
However, recently relegated outfits Wolves and West Ham are also said to be interested in him, and he has his pick of the top Championship clubs.
Saints are in the market for midfielders amid the likely exit of Shea Charles, 22, with Leeds United seriously interested in his signature.
