Fort de Chaudfontaine, Military fort in Chaudfontaine, Belgium.

Fort de Chaudfontaine is a military fort in Belgium with an irregular rectangular shape surrounded by a continuous ditch. The structure combines elements from the late 19th century with modern concrete components from early fortification techniques.

Built between 1881 and 1884 to General Henri Alexis Brialmont's plans, Fort de Chaudfontaine was one of twelve forts forming the Fortified Position of Liège, made of unreinforced concrete rather than masonry. On 13 August 1914 a shell set off an explosion in the 21 cm turret, killing at least 58 of the garrison and forcing surrender. Renovated and rearmed in 1933, it surrendered again on 16 May 1940 after Luftwaffe bombardment.

Just outside the main gate stands a small cemetery and war memorial holding 71 dead from 1914: two men from Fort de Fléron, ten killed in the intervals between the forts, and a civilian executed at Romsée. The fort itself now houses an adventure park.

The fort today functions as an adventure park offering active recreational activities for visitors throughout the year. The site is roughly 7 kilometers southeast of Liège and easily accessible.

The fort's guns fired black powder rather than smokeless powder, so choking gas spread through the confined firing spaces during action. The site also has an air intake tower added behind the fort in the 1930s, tall enough to draw clean air above possible gas clouds.