Fort de Charenton, Military fort in Maisons-Alfort, France

Fort de Charenton is a military fortification in Maisons-Alfort, southeast of Paris, built according to the polygonal defense principles of the 19th century. It consists of barracks, ramparts, and a surrounding ditch that together form a largely intact ensemble.

The fort was authorized by a law of 3 April 1841 proposed by Adolphe Thiers, then prime minister, as one of sixteen detached forts guarding Paris. Louis-Philippe laid the first stone on 19 April 1841, and the walls were finished the following year, with the completed fort in use by 1845. It cost 5 million francs and was used as a prison after the Revolution of 1848.

The fort's name comes from Charenton-le-Pont, the town it was meant to defend, though it stands in Maisons-Alfort. Since 1930 cavalry barracks of the Mobile Republican Guard have stood outside the walls along Boulevard Charles de Gaulle, ten of them still lining the boulevard. The site remains an active gendarmerie base.

The site is generally closed to the public due to its active military use. The best opportunity to visit is during the Journées du Patrimoine in September, when the fort opens its gates to outside visitors.

In August 1944, German troops planted explosive charges inside the fort, but specialist Henri-Marcel François defused them before they could be detonated. Thanks to this action, one of the few remaining intact fortifications from the Paris defensive ring survived.