Much had been expected of the 28-year-old after he swapped Roma for the south coast in August in a deal worth up to £14.6million.
The Italy international penned a four-year deal but has managed just 166 days at St Mary's, with Saints cutting their losses after an altercation with team-mate Jose Fonte last week.
"I've come to Italy's biggest club, and one of the biggest in Europe, in a World Cup year," he said.
"I want to enjoy this experience, do my best to be involved in the World Cup and stay here for many years."
Juventus confirmed in a statement that they have an option for a permanent deal.
"Juventus Football Club can today confirm that terms have been agreed with Southampton Football Club on a free loan deal for Pablo Daniel Osvaldo," the club said.
"The agreement also includes the option, to be exercised before May 13 2014, for the purchase of the player's full registration rights at a price of 19 million euros, to be paid over the course of three years."
That deal translates to £15.6million to Southampton and Press Association Sport understands the reigning Serie A champions will pay his wages in full during the loan.
Osvaldo's departure will be a relief to Southampton, with manager Mauricio Pochettino admitting on Thursday that it would be hard for him to play for the club again.
The Saints boss worked with the Argentina-born striker for just over a season at Espanyol and, when he signed, was quick to reassure fans that the controversies that had dogged his career were over.
However, Osvaldo attacked popular defender Fonte during a session at the club's Staplewood training ground and was handed a two-week suspension by the club.