Hadrian's Wall (Latin: Vallum Hadriani, also known as the Roman Wall, Picts' Wall, or Vallum Aelium in Latin) is a former defensive fortification of the Roman province of Britannia, begun in AD 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 of what is now northern England, it was a stone wall with large ditches in front and behind, stretching across the whole width of the island. Soldiers were garrisoned along the line of the wall in large forts, smaller milecastles, and intervening turrets. In addition to the wall's defensive military role, its gates may have been customs posts.

Hadrian's Wall Path generally runs close along the wall. Almost all the standing masonry of the wall was removed in early modern times and used for local roads and farmhouses. None of it stands to its original height, but modern work has exposed much of the footings, and some segments display a few courses of modern masonry reconstruction. Many of the excavated forts on or near the wall are open to the public, and various nearby museums present its history. The largest Roman archaeological feature in Britain, it runs a total of 73 miles (117.5 kilometres). Regarded as a British cultural icon, Hadrian's Wall is one of Britain's major ancient tourist attractions.