Bettencourt, 89, bought D’Arros Island along with several neighbouring islets for $18 million in 1998 and recently sold them for $60 million to a Seychelles-registered business, Housing and Habitat Minister Christian Lionnet said.
The stunning islands are located in the Indian Ocean, about 250 kilometres (155 miles) southwest of the main Seychelles island of Mahe.
The Seychelles-registered business that bought the islands is called the Chelomia Company Ltd, which is affiliated with the Geneva-based Save our Seas foundation.
The Seychelles government said in a statement that the islands would “soon be proclaimed a nature reserve” and “managed by the Save our Seas Foundation in direct collaboration with the Ministry of Environment and Energy.”
Bettencourt was the target of a French tax probe but tax authorities said last year they would not pursue criminal charges against her.
During the probe, she revealed more 100 million euros in undeclared funds in a dozen bank accounts including in Switzerland and Singapore, as well as the island property in the Seychelles.