Southsea is a seaside resort and geographic area, located in Portsmouth at the southern end of Portsea Island, Hampshire, England. Southsea is located to the south of Portsmouth city centre and to the east of Old Portsmouth. It developed as a fashionable Victorian seaside resort in the 19th century, originally named Croxton Town, but later adopting the name of nearby Southsea Castle, a seafront fort constructed in 1544 to help defend the Solent and approaches to Portsmouth Harbour.