A cannon is a large-caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder ("black powder") was the primary propellant before the invention of smokeless powder during the late 19th century. Cannons vary in gauge, effective range, mobility, rate of fire, angle of fire and firepower; different forms of cannon combine and balance these attributes in varying degrees, depending on their intended use on the battlefield. A cannon is a type of heavy artillery weapon.

The word cannon is derived from several languages, in which the original definition can usually be translated as tube, cane, or reed. In the modern era, the term cannon has fallen into decline, replaced by guns or artillery, if not a more specific term such as howitzer or mortar, except for high-caliber automatic weapons firing bigger rounds than machine guns, called autocannons.

The earliest known depiction of cannons appeared in Song dynasty China as early as the 12th century; however, solid archaeological and documentary evidence of cannons do not appear until the 13th century. In 1288 Yuan dynasty troops are recorded to have used hand cannon in combat, and the earliest extant cannon bearing a date of production comes from the same period. By the early 14th century, possible mentions of cannon had appeared in the Middle East and the depiction of one in Europe by 1326. Recorded usage of cannon began appearing almost immediately after. They subsequently spread to India, their usage on the subcontinent being first attested to in 1366. By the end of the 14th century, cannons were widespread throughout Eurasia. Cannons were used primarily as anti-infantry weapons until around 1374, when large cannons were recorded to have breached walls for the first time in Europe. Cannons featured prominently as siege weapons, and ever larger pieces appeared. In 1464 a 16,000 kg (35,000 lb) cannon known as the Great Turkish Bombard was created in the Ottoman Empire. Cannons as field artillery became more important after 1453, with the introduction of limber, which greatly improved cannon maneuverability and mobility. European cannons reached their longer, lighter, more accurate, and more efficient "classic form" around 1480. This classic European cannon design stayed relatively consistent in form with minor changes until the 1750s.