The woman, believed to be in her 20s, was flung overboard when her vessel struck a warning beacon on the river in the city of Avignon.
Officials said seven other people were on the boat with her and four were injured in the crash.
Two of them are in a serious condition and were rushed to Avignon hospital
An urgent investigation has been launched to determine the cause of the accident.
The official said the boat was travelling from the island of Barthelasse, where the victim had dinner with friends at a restaurant.
They were sailing to Avignon after having dinner.
Barthelasse is France’s largest river island.
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