Thousands of Corsicans marched on Saturday, ahead of a visit by President Emmanuel Macron next week.
They were demanding more autonomy for the French Mediterranean island.
The local prefecture said between 5,600 and 6,000 people marched peacefully in its capital, Ajaccio, while organisers put the number of protesters at between 22,000 and 25,000.
"It's a historic moment, a march of unprecedented proportions in Ajaccio," the island's chief Gilles Simeoni told reporters.
Other demands include limits on the rights of outsiders to buy property on the island and equal status for the French and Corsican languages.
The French government though has rejected several demands, leading to warnings that some return to violence on the island can't be excluded if Corsicans feel they are not being heard.
Before laying down arms in 2014, groups backing Corsican independence had carried out more than 10,000 attacks over four decades, blowing up police stations and holiday homes.
These clandestine groups were linked to at least 40 deaths, either in attacks on government officials or as a result of infighting among rival factions.