Portsmouth ( PORTS-məth) 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.

Portsmouth’s history can be traced to Roman times and has been a significant Royal Navy dockyard and base for centuries. Portsmouth was founded c. 1180 by Anglo-Norman merchant Jean de Gisors in the south-west area of Portsea Island, a location now known as Old Portsmouth. Around this time, de Gisors ordered the construction of a chapel dedicated to St Thomas Becket. This became a parish church by the 14th century. Portsmouth was established as a town with a royal charter on 2 May 1194. The city is home to the first drydock ever built. It was constructed by Henry VII in 1496.

Portsmouth was England’s first line of defence during an attempted French invasion in 1545 at the Battle of the Solent, famously notable for the sinking of the carrack Mary Rose and witnessed by King Henry VIII of England from Southsea Castle. Portsmouth has the world’s oldest dry dock, “The Great Stone Dock”; originally built in 1698, rebuilt in 1769 and presently known as “No.5 Dock”. The world’s first mass production line was established at the naval base’s Block Mills which produced pulley blocks for the Royal Navy fleet. By the early-19th century, Portsmouth was the most heavily fortified city in the world, and was considered “the world’s greatest naval port” at the height of the British Empire throughout Pax Britannica. By 1859, a ring of defensive land and sea forts, known as the Palmerston Forts had been built around Portsmouth in anticipation of an invasion from continental Europe.

In the 20th century, Portsmouth achieved city status on 21 April 1926. During the Second World War, the city was a pivotal embarkation point for the D-Day landings and was bombed extensively in the Portsmouth Blitz, which resulted in the deaths of 930 people. In 1982, a large Royal Navy task force departed from Portsmouth for the Falklands War. Her Majesty’s Yacht Britannia was formerly based in Portsmouth and oversaw the transfer of Hong Kong in 1997, after which Britannia was retired from royal service, decommissioned and relocated to Leith as a museum ship.

HMNB Portsmouth is an operational Royal Navy base and is home to two-thirds of the UK’s surface fleet. The base has long been nicknamed Pompey, a nickname it shares with the wider city of Portsmouth and Portsmouth Football Club. The naval base also contains the National Museum of the Royal Navy and Portsmouth Historic Dockyard; which has a collection of historic warships, including the Mary Rose, Lord Nelson’s flagship, HMS Victory (the world’s oldest naval ship still in commission), and HMS Warrior, the Royal Navy’s first ironclad warship.