Portsmouth is a port city and unitary authority located in Hampshire, England. It is situated on Portsea Island off the south coast of England in the Solent. Notably, it is the only city in England that is not located primarily on the mainland.
The city is positioned approximately 22 miles southeast of Southampton, 50 miles west of Brighton and Hove, and 74 miles southwest of London. It forms part of the South Hampshire urban area alongside Gosport, Fareham, Havant, Eastleigh, and Southampton.
With a recorded population of 208,100, Portsmouth is recognized as the most densely populated city in the United Kingdom.