Plymouth ( (listen)) is a port city and unitary authority in South West England. It is located on the south coast of Devon, approximately 36 miles (58 km) south-west of Exeter and 193 miles (311 km) south-west of London. It is bordered by Cornwall to the west and south-west.

Plymouth's early history extends to the Bronze Age when a first settlement emerged at Mount Batten. This settlement continued as a trading post for the Roman Empire, until it was surpassed by the more prosperous village of Sutton founded in the ninth century, now called Plymouth. In 1588, an English fleet based in Plymouth intercepted and defeated the Spanish Armada. In 1620, the Pilgrim Fathers departed Plymouth for the New World and established Plymouth Colony, the second English settlement in what is now the United States of America. During the English Civil War, the town was held by the Parliamentarians and was besieged between 1642 and 1646.

Throughout the Industrial Revolution, Plymouth grew as a commercial shipping port, handling imports and passengers from the Americas, and exporting local minerals (tin, copper, lime, china clay and arsenic). The neighbouring town of Devonport became strategically important to the Royal Navy for its shipyards and dockyards. In 1914, three neighbouring independent towns, viz. the county borough of Plymouth, the County Borough of Devonport, and the urban district of East Stonehouse were merged, becoming the County Borough of Plymouth. In 1928, it achieved city status. During World War II, due to the city's naval importance, the German military targeted and partially destroyed the city by bombing, an act known as the Plymouth Blitz. After the war, the city centre was completely rebuilt. Subsequent expansion led to the incorporation of Plympton, Plymstock, and other outlying suburbs, in 1967.

The city is home to 264,695 (2021) people, making it the 30th-most populous built-up area in the United Kingdom and the second-largest city in the South West, after Bristol. It is governed locally by Plymouth City Council and is represented nationally by two MPs. Plymouth's economy remains strongly influenced by shipbuilding and seafaring but has tended toward a service economy since the 1990s. It has ferry links to Brittany (Roscoff and St Malo) and to Spain (Santander). It has the largest operational naval base in Western Europe, HMNB Devonport, and is home to the University of Plymouth. Plymouth is categorized as a Small-Port City using the Southampton System for port-city classification.