Fort Saint Louis, Military fortress in Fort-de-France, Martinique.

Fort Saint Louis is a Vauban-style fortress on a rocky peninsula at the mouth of Fort-de-France Bay. Its lower seaward face is built of grey-brown masonry rising straight from the water, while above lies a raised grassy level edged by a lower stone parapet. A long crenellated rampart runs along the top of a grassy embankment, and near the waterline stands a long stone building with a row of arched openings and a dark roof.

Jacques Dyel du Parquet had wooden palisades built on the rocky peninsula around 1638. After the fort was destroyed, Louis XIV appointed Jean-Charles de Baas governor-general and had it rebuilt in 1669; the Count of Blénac then gave it its Vauban form, with a 487-metre wall four metres high and two metres thick. In July 1674 the fort withstood a three-day attack by Admiral de Ruyter's Dutch fleet.

The fort's name honours Louis XIV, who ordered its reinforcement in 1672; it became Fort Louis in 1680 under the Count of Blénac, who made it the seat of the Royal Pavilion and the Sovereign Council. The site later housed a zoo, and its last residents, common iguanas, still live within the walls. Visitors can see structures named after Aycard, de Baas, de Gemozat and d'Amblimont, defenders during the 1674 Dutch siege.

The fort is generally open to visitors, but some areas remain off-limits since the French Navy still uses the site. It is best to check current conditions before visiting and wear sturdy footwear, as the ground is uneven.

The fort's green iguanas (Iguana iguana) are not native to Martinique; they are thought to have reached the site by boat from French Guiana or the Îles des Saintes. They must stay inside the walls, since interbreeding with the endemic Iguana delicatissima of the Lesser Antilles could produce hybrids, as happened in Guadeloupe and Les Saintes.