Flat Bastion is a bastion which projects southward from the Charles V Wall in the British Overseas Territory of Gibraltar. Once known as the St. Jago's Bastion or the Baluarte de Santiago in Spanish,
Model of Gibraltar (1865) demonstrates the Charles V Wall to the left of center. Along and on the right (south side) of the wall, from front to back, are included: South Bastion (extending into the harbour), Southport Gates, Trafalgar Cemetery, Prince Edward's Gate, and Flat Bastion.