Marseilless top Jewish leader Zvi Ammar said on Tuesday a synagogue called Or Thora in Marseilles is to be converted into a mosque, reflecting demographic shifts in the southern French city.
"For the past 20 years or so we have seen the shift of the Jewish community to other neighbourhoods," Ammar said, adding that he viewed the sale "positively."
"We all have the same God, the main thing is for this to proceed in harmony," he said.
The site near the city's main rail station was built as Jews flocked to Marseilles from Algeria after the north African country gained independence from France in 1962 following an eight-year war, he noted.
Al Badr currently runs a mosque nearby that is too small for its congregation.
Marseille's Jewish community is thriving, Ammar said, with the number of synagogues nearly doubling to 58 from 32 over the last three decades.
The city's 70,000 Jews make up one of France's -- and Europe's -- largest Jewish communities.
Marseille's population of nearly two million also counts around 220,000 Muslims, of whom 70,000 are practising.
Marseille's Muslims are still awaiting the construction of a Grand Mosque, but the project promised by the city's mayor in 2001 is mired in financial woes as well as legal challenges by the far-right National Front.
At an estimated cost of some 23 million euros ($26 million), the mosque would be France's largest if the project is finally achieved.
Earlier this week the mayor of Nice, just along the French Riviera from Marseilles, secured a green light to sue the French state in a bid to block the opening of a Saudi-funded mosque in the city.
Mayor Christian Estrosi has accused the building's owner, Saudi Arabia's Islamic Affairs Minister Sheikh Saleh bin Abdulaziz, of "advocating Sharia" and wanting to "destroy all of the churches on the Arabian peninsula."