Hadrian's Wall is a stone and turf fortification built by the Roman Empire across the width of modern-day England. It was the second of three similar fortifications built across Great Britain, the first being Gask Ridge and the last the Antonine Wall. All three were built to prevent military raids by the Pictish tribes to the north (ancient inhabitants of Scotland). It was also to physically mark the frontier of the Empire. Hadrian's Wall is the best known of the three because its physical presence remains most evident today.

The wall marked the northern border in Britain, also the most heavily fortified in the Empire. In addition to its use as a military fortification, the gates through the wall would also have served as customs posts to allow trade taxation.

A significant portion of the wall still exists, particularly the mid-section, and for much of its length the wall can be followed on foot. It's the most popular tourist attraction in Northern England, where it is often known simply as the Roman Wall. It was made a UNESCO World Heritage Site in 1987.