Fort du Saint-Eynard, Military fort in Le Sappey-en-Chartreuse, France.

Fort du Saint-Eynard is a fortified structure at 1338 meters elevation with stone walls overlooking the Belledonne massif and Grésivaudan valley near Grenoble. The fort was designed to command views of the valleys and mountainous terrain surrounding the region.

The fort was constructed in the 19th century as part of the Grenoble fortified belt. This installation formed part of a series of defensive works built to protect the strategic alpine region.

The fort's name comes from Saint Eynard, a Carthusian monk of the Chartreuse massif. The chapel at the entrance occupies the spot where carrier pigeons were once kept, and the optical telegraph on the west building's facade was an early alternative to pigeon post. Today the site hosts a restaurant, an exhibition and meeting rooms.

The fort is open to visitors from May through November, with guided tours offered on weekends. A restaurant on site serves regional mountain specialties for those spending time at the location.

The structure incorporates rainwater collection systems while preserving its original 19th-century military design. This combination of historical protection and modern resource management demonstrates how historic fortifications can be adapted for contemporary use.