Forte Sangallo is a fortress located by the sea near the historic village of Nettuno.

It was Cesare Borgia who wanted the construction in the early 1500s of this fortress to defend the strategic port of Neptune, on behalf of his father, at that time pontiff (Alexander the Sixth), commissioning the work from Giuliano da Sangallo whose designs, however, were reviewed by his brother and architect Antonio da Sangallo the Elder (after whom it is named).