Southsea is a seaside resort and a geographic area of Portsmouth, Portsea Island in the ceremonial county of Hampshire, England. Southsea is located 1.8 miles (2.8 km) to the south of Portsmouth's inner city-centre.

Portsmouth is a port city and unitary authority in Hampshire, England. Most of Portsmouth is located on Portsea Island, off the south coast of England in the Solent. This means Portsmouth is the only English city not located primarily on the mainland. Located 74 miles (119 km) south-west of London, 50 miles (80 km) west of Brighton and Hove, and 22 miles (35 km) south-east of Southampton; Portsmouth is part of the South Hampshire conurbation. It is the most densely populated city in the United Kingdom, with a population last recorded at 208,100.