Gâtinais (French pronunciation: [ɡɑtinɛ]; or Gâtine) was a province of France, containing the area around the valley of the Loing, corresponding roughly to the northeastern part of the départment of Loiret, and the south of the present departments Seine-et-Marne. Under the Bourbons, the Gâtinais had already been divided between the provinces of Île-de-France and Orléans. In the words of the modern tourist slogan for the "two Gâtinais", it lies between the Seine and the Loire.

Under the Franks, Gâtinais was the pagus Wastinensis (eventually to become Wasteney in the 20th Century), (or Vastinensis) one of five belonging to the Archbishop of Sens. Puisaye, and the archbishop's other fiefs in the northwest of the modern department of Yonne, west of the river, are also often considered part of Gâtinais; as is the area around Étampes in the present department of Essonne.

The capital of the province was Château-Landon, and a twenty-five mile circle around Notre-Dame de Château-Landon would basically comprise it. The western part, Gâtinais orléanais, would correspond to the arrondissements of Montargis and a large part of Pithiviers, in Loiret. The eastern part, Gâtinais français, had Nemours as its chief town, and corresponds to the arrondissement of Fontainebleau in Seine-et-Marne.