Lawmakers and civil society groups from both countries have written to French President Francois Hollande, calling for the return of “colonial treasures”, including royal thrones and swords.
Many are now on display in French museums, including the Quai Branly in Paris, which exhibits indigenous art from across the world.
Signatories to the open letter, which was published this week, described the objects as having “an exceptional spiritual and proprietary value for the Benin people”.
France ruled Dahomey until 1960, when it was granted independence and changed its name to Benin. Dahomey included the kingdom of the same name that dates back to about 1600.
Most of the artefacts have not been documented but Benin’s ambassador to the UN cultural body UNESCO in Paris, Irenee Zevounou, believes some 4,500 to 6,000 are in France, including in private collections.
France’s stockpiling of treasures from Dahomey happened during colonial fighting between 1892 and 1894 but also by missionaries who “robbed communities of what they considered to be charms”, said Zevounou.
“The negotiations are both with the French state and the French church”, he added.