A duelling pistol is a type of pistol that was manufactured in matching pairs to be used in a duel, when duels were customary. Duelling pistols are often single-shot flintlock or percussion black-powder pistols which fire a lead ball. Not all fine, antique pairs of pistols are duelling pistols, though they may be called so.

Until the mid-18th century, duels were typically fought with swords. In London, the first recorded pistol duel was in 1711, but the use of pistols was unusual until the 1760s. Thereafter they quickly took over, and after 1785 it was rare for a sword duel to be fought in London. From about 1770 onwards, gunsmiths were producing pistols expressly made for duelling.

Unless precisely tuned, standard flintlock pistols can have a noticeable delay between pulling the trigger and actually firing the projectile. Purpose-built duelling pistols have various improvements to make them more reliable and accurate.

Duelling pistols have long and heavy barrels—the added weight helps steady aim and reduce recoil. The barrels on earlier guns were cylindrical, while later ones tended to be octagonal. The barrels were given a blued or browned finish to reduce glare. Spurs on the trigger guards began appearing after around 1805 to provide a rest for the middle finger to improve the shooter's grip. Other features were saw handles, platinum-lined touch-holes and hair triggers. Reliability was important because if a duellist's pistol failed to fire, he was considered to have taken his shot and was not permitted to re-cock the pistol and try again.

All component parts were manufactured, hand-finished, and then adjusted with great care and precision, which made duelling pistols much more costly than standard firearms of the period. Special care was taken when moulding the lead bullets to ensure that there were no voids which would affect accuracy. In some duels, the pistols were carefully and identically loaded, and each duellist was offered his choice of the indistinguishable loaded pistols; conversely, sometimes the duellists would use their own pistols and so the weapons would be different.

As duels were generally fought at short distances which were paced out, typically 35 to 45 feet (11 to 14 m), between stationary opponents, extreme accuracy was not required.

Duelling pistols had long barrels – typically around 10 in (250 mm), and fired large, heavy bullets. Pistols with calibers of 0.45 in (11 mm), 0.52 in (13 mm), 0.58 in (15 mm) or even 0.65 in (17 mm) were common. The bullets loaded in them could weigh 214 grains (0.49 ounces; 13.9 grams) in .52 caliber, or more in larger calibers. Injuries from such bullets, coupled with the primitive state of emergency medicine at the time when duels were commonplace, meant that pistol duels frequently resulted in fatalities, often some hours or days afterwards.

Most English pistols had smooth bores, though some had scratch rifling, a subtle form of rifling which was difficult to see with the naked eye. Pistols with rifled barrels spin-stabilize the shot when it is fired, resulting in much improved accuracy. As a result, duelling pistols with rifled barrels were considered unsporting by many, although there was no unfairness so long as the pistols were identical. The rifling either consisted of a large number of very shallow grooves known as scratch rifling or rifling that stopped short of the end of the pistol known as French rifling. For some in the eighteenth century, duelling with less-accurate, smooth-bore weapons was preferred as they viewed it as allowing the judgement of God to take a role in deciding the outcome of the encounter.