The Fort de Châtillon was a fortification located about 5 kilometres (3.1 mi) south of Paris in the communes of Châtillon-sous-Bagneux and Fontenay-aux-Roses.

The fort was named for the town it was designed to protect, Châtillon-sous-Bagneux, but the greater portion of the site is actually within Fontenay-aux-Roses.

Unlike other Parisian fortifications, the new fort was designed for action in all directions, as the location commanded much of the surrounding region.

The fort featured a number of internal traverses, mounded dikes intended as shelters against low-angle shellfire from a variety of directions.

After the French Liberation, convicted collaborators Joseph Darnand and Jean Hérold-Paquis were executed by firing squad at the fort.

A portion of the building that housed Zoé became the Museum of the Atom, while the remainder was dedicated to research into the life sciences.