The Flat Bastion is a bastion which projects southward from the Charles V Wall in the British Overseas Territory of Gibraltar. At one time known as St. Jago's Bastion or the Baluarte de Santiago in Spanish, its construction was begun by the Spanish in the mid 16th century. The fortification formed part of the southern defences of the city of Gibraltar, together with Charles V Wall and, to its west, Southport Gate, Southport Ditch, and South Bastion. Flat Bastion takes its name from the angle that its south-facing walls form with each other and with the Charles V Wall. Within the eastern portion of the Flat Bastion is the Flat Bastion Magazine. The bastion and magazine within it are separately listed with the Gibraltar Heritage Trust. The magazine has been restored and converted into a rese