The Saints are waiting on the formalities of a deal to be completed, with a medical expected to take place on Monday.
The package being put in place includes an additional €2m in bonus payments.
The 23-year-old finds himself on the move after struggling to make the desired impact at Juventus.
He initially moved to Turin on loan in the summer of 2015, from French side Marseille, with that agreement later made permanent.
The Gabon international has, however, been restricted to 42 appearances in two seasons for the reigning Serie A champions.He will now be hoping to see more minutes with Southampton, with Mauricio Pellegrino’s side set to seal a transfer before the start of the new Premier League season.