Castillo de Santa Catalina del Puerto is a 16th-century fortification in El Puerto de Santa María, Cádiz, constructed to defend the entrance to the Bay of Cádiz through coordinated crossfire with the neighbouring Castillo de San Felipe. Though ordered by Charles V in 1540, construction did not commence until 1585, with the tower representing the earliest structure. The fortress played a critical military role during the Peninsular Wars, serving French occupation forces between 1810 and 1812 during the siege of Cádiz. Recognised as a Spanish historical monument through decree and Andalusian heritage legislation, the castle is also designated a Historic Site related to the 1812 Constitution, reflecting its significance to Spanish constitutional history.
