Gros îlet is an uninhabited islet in the Trois-Îlets commune. It is also called Îlet Mandoline because of its shape. It is located in the Baie de Génipa, opposite Pointe Vatable in Trois-Ilets.
It is around 600 meters long.
Formerly known as Îlet à Vaches (Islet of cows) because a farming family used to let their cows graze there, it is now privately owned.
It is also part of the Parc Naturel Régional de Martinique.
A bank of gravel and madreporic rocks, covered only by two or three feet of water, surrounds Gros-Îlet in its western part and extends five and a half cables to the Pointe de la Rose side.