"Immobile expressed his wish to devote most of his time to his loved ones after 17 years as a professional," the French club said in a statement.
The 36-year-old striker joined Paris FC from Bologna in February and made 12 Ligue 1 appearances, scoring twice.
He scored 306 goals in 599 club matches in all competitions, also netting 17 times in 57 appearances for Italy.
The forward was part of Italy's Euro-winning squad in 2020 and scored twice during the tournament, which concluded with victory over England in the final at Wembley in July 2021, with the tournament being postponed by a year because of the COVID-19 pandemic.
Immobile enjoyed his greatest success during his eight seasons at Lazio, becoming the club's all-time leading scorer with 207 goals in 340 appearances. He won the Coppa Italia and two Italian Super Cups with the Rome-based club.
In 2020, he won the European Golden Shoe after equalling Gonzalo Higuain's single-season league record of 36 Serie A goals, and he finished as the league's leading scorer four times.
He also played for Italian clubs Juventus, Pescara, Genoa and Torino, Germany's Borussia Dortmund, Spain's Sevilla and Turkish side Besiktas.