The release of Olivier Grondeau on Thursday comes as France and the rest of Europe try to pursue negotiations with Iran over its rapidly advancing nuclear program.
US President Donald Trump, meanwhile, has sent his own letter to Iran's 85-year-old Supreme Leader Ayatollah Ali Khamenei to jump-start talks.
Trump is also pressuring Tehran over its support of Yemen's Houthi rebels as the American military has launched an intense new campaign of air strikes targeting the group.
French President Emmanuel Macron wrote online that Grondeau had been freed.
He offered no immediate details of what led to Grondeau's release, though it came on Nowruz, the Persian New Year, when Iran has released prisoners in the past.
Jean-Noel Barrot, France's minister for Europe and foreign affairs, posted a picture online of Grondeau smiling aboard what appeared to be a private jet.
"We will tirelessly continue our efforts to ensure that all our compatriots still held hostage, including Cecile Kohler and Jacques Paris, are in turn released," Barrot wrote.
Macron also raised the case of the other two French nationals held in Iran.
"Cecile Kohler and Jacques Paris must be freed from Iranian jails," he wrote.
"My thoughts are with them and their families today."
The Iranian government did not immediately acknowledge Grondeau's release.
Such releases of Westerners in Iran typically come in exchange for something.
Early this week, foreign ministry spokesman Esmail Baghaei said France had arrested an Iranian women who supported Palestinians, but said Tehran was still trying to gather more details about her case.
Grondeau was detained by Iranian authorities in October 2022 in the city of Shiraz.
An Iranian court later sentenced the backpacker and world traveller to five years in prison on espionage charges that he, his family and the French government vigorously denied.
He had been held at Tehran's notorious Evin prison, which holds Westerners, dual nationals and political prisoners often used by Tehran as bargaining chips in negotiations with the West.
19°C