The Fort of São Bruno is situated on the estuary of the River Tagus in Caxias, Oeiras municipality, near Lisbon in Portugal.

[1][2] During the Portuguese Restoration War, King John IV of Portugal identified the need to strengthen Lisbon's defences in the face of attacks by the Spanish navy.

[3][4] Built on a rocky outcrop into the river estuary, the Fort of São Bruno (taking its name from a nearby convent) is in the shape of a star around a raised central square.

The Guarda Fiscal was responsible for it until 1946, although in 1941 it was used as a sailing centre by the Mocidade Portuguesa, a youth organization of the right-wing Estado Novo Government.

A well-supported campaign in 1999-2000 for the restoration of the fort and improvements to the surrounding area led to significant work being carried out by the Oeiras municipality.