Bristol (/ˈbrɪstəl/ ^ⓘ) is a cathedral city, unitary authority area and ceremonial county in South West England, the most populous city in the region. Built around the River Avon, it is bordered by the ceremonial counties of Gloucestershire to the north and Somerset to the south. The county is in the West of England combined authority area, which includes the Greater Bristol area (eleventh most populous urban area in the United Kingdom) and nearby places such as Bath. Bristol is the second largest city in Southern England, after the capital London.

Iron Age hillforts and Roman villas were built near the confluence of the rivers Frome and Avon. Bristol received a royal charter in 1155 and was historically divided between Gloucestershire and Somerset until 1373 when it became a county corporate. From the 13th to the 18th century, Bristol was among the top three English cities, after London, in tax receipts. A major port, Bristol was a starting place for early voyages of exploration to the New World. At the height of the Bristol slave trade, from 1700 to 1807, more than 2,000 slave ships carried an estimated 500,000 people from Africa to slavery in the Americas. The Port of Bristol has since moved from Bristol Harbour in the city centre to the Severn Estuary at Avonmouth and Royal Portbury Dock.

The city's modern economy is built on the creative media, electronics and aerospace industries; the city-centre docks have been redeveloped as cultural and heritage centres. There are a variety of artistic and sporting organisations and venues including the Royal West of England Academy, the Arnolfini, Ashton Gate and the Memorial Ground. The city has two universities; the University of Bristol and the University of the West of England (UWE Bristol). It is connected to the world by Bristol Airport; to the rest of the Great Britain via Bristol Temple Meads and Bristol Parkway mainline rail stations; by road by both the south-west to West Midlands M5 and the London to South Wales M4 (which connect to the city centre by the Portway and M32).

The name derives from the Old English Brycgstow, meaning "assembly place by the bridge" or simply "site of the bridge", presumably in reference to a crossing over the Avon. The final l is an unetymological addition that first appears in the 12th century, which may be due to the unique "Terminal L" found in the Bristol dialect. An older form of the name survives as the surname Bristow, which is derived from the city.

Archaeological finds, including flint tools believed to be between 300,000 and 126,000 years old made with the Levallois technique, indicate the presence of Neanderthals in the Shirehampton and St Annes areas of Bristol during the Middle Palaeolithic. Iron Age hill forts near the city are at Leigh Woods and Clifton Down, on the side of the Avon Gorge, and on Kings Weston Hill near Henbury. A Roman port, Portus Abonae (Avonport) – abbreviated to Abona in the Antonine Itinerary, existed at what is now Sea Mills (connected to Bath and Gloucester by Roman roads); another settlement was at the present-day Inns Court. Isolated Roman villas and small forts and settlements were also scattered throughout the area.

Bristol was founded by 1000; by about 1020, it was a trading centre with a mint producing silver pennies bearing its name. By 1067, Brycgstow was a well-fortified burh, and that year the townsmen beat back a raiding party from Ireland led by three of Harold Godwinson's sons. Under Norman rule, the town had one of the strongest castles in southern England. Bristol was the place of exile for Diarmait Mac Murchada, the Irish king of Leinster, after being overthrown. The Bristol merchants subsequently played a prominent role in funding Richard Strongbow de Clare and the Norman invasion of Ireland.

The port developed in the 11th century around the confluence of the Rivers Frome and Avon, adjacent to Bristol Bridge just outside the town walls. By the 12th century, there was an important Jewish community in Bristol which survived through to the late 13th century when all Jews were expelled from England. The stone bridge built in 1247 was replaced by the current bridge during the 1760s. The town incorporated neighbouring suburbs and became a county in 1373, the first town in England to be given this status. During this period, Bristol became a shipbuilding and manufacturing centre. By the 14th century, Bristol, York and Norwich were England's largest medieval towns after London. One-third to one-half of the population died in the Black Death of 1348–49, which checked population growth, and its population remained between 10,000 and 12,000 for most of the 15th and 16th centuries.

During the 15th century, Bristol was the second most important port in the country, trading with Ireland, Iceland and Gascony. It was the starting point for many voyages, including Robert Sturmy's (1457–58) unsuccessful attempt to break the Italian monopoly of Eastern Mediterranean trade. New exploration voyages were launched by Venetian John Cabot, who in 1497 made landfall in North America. A 1499 voyage, led by merchant William Weston of Bristol, was the first expedition commanded by an Englishman to North America. During the first decade of the 16th century Bristol's merchants undertook a series of exploration voyages to North America and even founded a commercial organisation, 'The Company Adventurers to the New Found Land', to assist their endeavours. However, they seem to have lost interest in North America after 1509, having incurred great expenses and made little profit.