Hadrian's Wall, also known as the Roman Wall, Picts' Wall, or Vallum Hadriani in Latin, is a former defensive fortification of the Roman province of Britannia, begun in CE 122 in the reign of the emperor Hadrian. Running "from Wallsend on the River Tyne in the east to Bowness-on-Solway in the west", the Wall covered the whole width of the island. In addition to the wall's defensive military role, its gates may have been customs posts.

A significant portion of the wall still stands and can be followed on foot along the adjoining Hadrian's Wall Path. The largest Roman archaeological feature in Britain, it runs a total of 73 miles (117.5 kilometres) in northern England. Regarded as a British cultural icon, Hadrian's Wall is one of Britain's major ancient tourist attractions. It was designated as a UNESCO World Heritage Site in 1987. In comparison, the Antonine Wall, thought by some to be based on Hadrian's wall, was not declared a World Heritage site until 2008.Hadrian's Wall marked the boundary between Roman Britannia and unconquered Caledonia to the north. The wall lies entirely within England and has never formed the Anglo-Scottish border.