Castle ward comprises Swansea city centre and areas to its west and north. The ward is bounded to the east by the River Tawe and to the south by Swansea Bay. Parts of the ward are in Communities First West and South Cluster areas, and parts are within the Vibrant and Viable Places programme. The ward covers 308 hectares, with a population density of 51.6 people per hectare.
Major employers include City & County of Swansea, BT, Grwp Gwalia Cyf, Swansea Housing Association, UWTSD, HM Prison Service, Tesco, Sainsbury, Debenhams, Marks and Spencer, and other city centre businesses.
Also within the ward are Swansea train station, Parc Tawe shopping centre, Swansea Museum, the National Waterfront Museum and the Maritime Quarter. Major residential areas include Sandfields, Mount Pleasant and Waun Wen.
Neighbouring wards are Uplands, Townhill, Cwmbwrla, Landore and St. Thomas.