Fort de Chillon, Military fortification in canton Vaud, Switzerland

Fort de Chillon is a mixed infantry-artillery fort built in 1941–1942 almost entirely underground in the steep slope rising to Veytaux, above the rail line and spanned by the Viaduc de Chillon. Designated A390, it held 75 mm guns later replaced by 90 mm anti-tank guns, plus machine guns and 81 mm mortars. Infantry bunkers linked by underground galleries command the road and rail lines beside the castle.

The fort opened in 1942 as part of Switzerland's defense strategy during World War II. A garrison of approximately 130 soldiers from Mountain Brigade 10 was stationed there to protect the country from potential threats.

The fort's name comes from the neighbouring Château de Chillon, whose gardens held the first field fortifications in 1939. Since December 2020 an interactive museum has occupied the galleries, and guided tours can be combined with a visit to the castle across the road. The site also hosts cultural events and private wine cellars.

The fort is accessible through guided tours where visitors can explore the underground tunnels, gun positions, and living quarters. It is advisable to wear sturdy footwear, as the ground is uneven and some stairs are quite steep.

The fort was designated A390 in the Swiss fortification nomenclature, and its garrison numbered 131 men. Nine detached infantry bunkers defended the surface installation, linked to the main fort by underground galleries. The position was covered by the artillery of Fort de Champillon, above Aigle.