Portsea Island is a flat, low-lying island measuring 24.542km2 in area, just off the southern coast of England. The island is located within the traditional and ceremonial county of Hampshire and contains the vast majority of the city of Portsmouth. Portsea Island has the third largest population of all the islands in the British Isles after the mainlands of Great Britain and Ireland; it also has the highest population density. To the east of Portsea Island lies Hayling Island, separated by Langstone Harbour. To the west is the peninsular mainland town of Gosport, separated by Portsmouth Harbour. To the south, it faces into the Spithead area of the wider Solent. A narrow tidal channel along the northern edge of Portsea Island, known as Portsbridge Creek, separates Portsea Island from the mainland. Three main road bridges (from west to east: the M275 motorway, the A3 and the A2030) connect the island to the mainland road network. There is also a minor pedestrian and bicycle bridge and a small road bridge that connects Portsea Island to Whale Island, a restricted Royal Navy shorebase establishment within Portsmouth Harbour. Portsea Island has four railway stations (Portsmouth Harbour, Portsmouth & Southsea, Fratton and Hilsea) connected by an island branchline to the mainland railway network via a short railway bridge at Portsbridge Creek. In addition there are ferry services to Gosport (on the mainland), Hayling Island and the Isle of Wight. There are also ferries to the Channel Islands, northern France and northern Spain. Portsea Island gives its name to a relatively commercial and historic neighbourhood (adjoining the south-western "city centre") of Portsmouth known as Portsea, which has had variable use in local government but has long been a parish of the island.
