Château Sainte-Agathe, Military fortress in Porquerolles Island, France

Château Sainte-Agathe is a fortification situated on a hilltop on Porquerolles Island, constructed to defend the coastal settlement against attacks from the sea. The structure contains a cylindrical artillery tower with two levels linked by a central opening, featuring a circular vaulted chamber and an open rooftop platform.

The sources document the fort as state property inscribed as a monument historique on 14 December 1927; they give no construction date, royal patron or Napoleonic rebuilding. Its known elements are an artillery tower, an enclosing wall forming the main body of the place, and an outwork. The tower has two levels linked by an oculus at the vault's summit.

The fort is named after Saint Agatha, a Christian martyr from Catania, Sicily, whose cult was widespread in Provence. The name links the defensive structure to a religious dedication rather than to a local secular figure. The site is owned by the French state and has been listed as a monument historique since 14 December 1927.

The site is a French state property on Porquerolles, in the commune of Hyères, and has been a listed monument historique since 14 December 1927. Access is on foot, and the ensemble is read in three parts: the cylindrical artillery tower, the enceinte forming the main body of the place, and the forward projection. The tower's two levels connect only through an oculus pierced at the top of the vault, so the upper platform is reached from the vaulted circular hall below.

The fort is a French state property listed as a monument historique since 14 December 1927. Its tower has two levels joined by an oculus pierced at the top of the vault, so the circular domed hall below connects to the open-air platform above through that single opening.