Fort des Sept-Îles, Historic fort in Perros-Guirec, France.

Fort des Sept-Îles occupies the western part of Île aux Moines in the Sept-Îles archipelago. Its main block is a tall, roughly square tower of rough-cut stone in grey, tan and brown, with a flat top edged by a thin metal railing, a small rectangular window on the left face and a narrow vertical slit on the right. A smaller gabled stone building abuts it on the left, and a curved stone wall runs along the lower right above the grass and the sea.

Louis XIV ordered a Vauban disciple to design the fort in 1694 to keep pirates who used the archipelago as a refuge away from nearby coasts. Plans of 1718 and 1739 provided batteries, a redoubt, barracks, a powder magazine and a vegetable garden, but building only began in 1740. Jean-Siméon Garangeau, engineer of the King and director of the fortifications of Saint-Malo, drew his last fort here; Jean-Baptiste Joseph Parrocel completed it in 1746.

The fort's name comes from the Sept-Îles archipelago, and the site has been listed as a monument historique since 1975, with a new listing issued on 26 August 2024 covering the fort, the old barracks, the Cosmoguer battery, four other batteries and two lines of entrenchments. The buildings belong to the Conservatoire du littoral, and the island has been a nature reserve since 1912.

Accessible only by boat excursions departing from Perros-Guirec or Trégastel, visits last approximately two hours and accommodate visitors with reduced mobility upon advance reservation.

The fort is located within France's oldest ornithological reserve, hosting over 27 breeding bird species including the country's only colony of northern gannets on Rouzic island.