"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 2020-winning squad 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 due to 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 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 Serie A'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.