The Argentina-born attacker returns to Serie A after just six months in the Premier League and will continue his career with the Italian club.
The Serie A champion was keen to add some more depth to the attack as the club chases its third consecutive Scudetto and head coach Antonio Conte sees the former Roma man as a valuable addition to his squad.
Osvaldo has fallen out of favor at Southampton following a training ground incident in which he became embroiled in a fight with defender Jose Fonte.
That incident saw him suspended for two weeks and he will now continue his career at Juventus as he aims to play his way into Italy's World Cup squad.
The 28-year-old joined Southampton from Roma at the start of the 2013-14 campaign and has since scored three goals in 13 Premier League appearances.
The striker previously enjoyed spells in Italy at Atalanta, Lecce, Fiorentina, Bologna and Roma, while also wearing the jerseys of Huracan and Espanyol.
He has a contract with Southampton until June 2017.