Dao (pronunciation: [táʊ], English approximation: /daʊ/ dow, Chinese: 刀; pinyin: dāo; jyutping: dou1) are single-edged Chinese swords, primarily used for slashing and chopping. They can be straight or curved. The most common form is also known as the Chinese sabre, although those with wider blades are sometimes referred to as Chinese broadswords. In China, the dao is considered one of the four traditional weapons, along with the gun (stick or staff), qiang (spear), and the jian (double-edged sword), called in this group "The General of Weapons".

In Chinese, the word 刀 can be applied to any weapon with a single-edged blade and usually refers to knives. Because of this, the term is sometimes translated as knife or sword-knife. Nonetheless, within Chinese martial arts and in military contexts, the larger "sword" versions of the dao are usually intended.^{[citation needed]}

While the dao have varied greatly over the centuries, most single-handed dao of the Ming period and later, and the modern swords based on them share several characteristics. Dao blades are moderately curved and single-edged, though often with a few inches of the back edge sharpened; the moderate curve allows them to be reasonably effective in the thrust. Hilts are sometimes canted, curving in the opposite direction of the blade, which improves handling in some forms of cuts and thrusts. The cord is usually wrapped over the wood of the handle. Hilts may also be pierced like those of jian (straight-bladed Chinese sword) for the addition of lanyards. However, modern swords for performances will often have tassels or scarves instead. Guards are typically disc-shaped and often cupped. This was to prevent rainwater from getting into the sheath and blood dripping down to the handle, making it more difficult to grip. Sometimes guards are thinner pieces of metal with an s-curve, the lower limb of the curve protecting the user's knuckles; very rarely, they may have guards like those of the jian.

Other variations to the basic pattern include the large bagua dao and the long-handled pudao.

The earliest dao date from the Shang dynasty in China's Bronze Age, and are known as zhibeidao (直背刀) – straight-backed knives. As the name implies, these were straight-bladed or slightly curved weapons with a single edge. Originally bronze, these weapons were made of iron or steel by the time of the late Warring States period as metallurgical knowledge became sufficiently advanced to control the carbon content. Originally less common as a military weapon than the jian – the straight, double-edged blade of China – the dao became popular with cavalry during the Han dynasty due to its sturdiness, superiority as a chopping weapon, and relative ease of use – it was generally said that it takes a week to attain competence with a dao/saber, a month to attain competence with a qiang/spear, and a year to attain competence with a jian/straight sword. Soon after dao began to be issued to infantry, beginning the replacement of the jian as a standard-issue weapon. Late Han dynasty dao had round grips and ring-shaped pommels, and ranged between 85 and 114 centimeters in length. These weapons were used alongside rectangular shields.

By the end of the Three Kingdoms period, the single-edged dao had almost completely replaced the jian on the battlefield. The jian subsequently became known as a weapon of self-defense for the scholarly aristocratic class, worn as part of court dress.

As in the preceding dynasties, Tang dynasty dao were straight along the entire length of the blade. Single-handed peidao ("belt dao") were the most common sidearm in the Tang dynasty. These became known as hengdao ("horizontal dao" or "cross dao") from the preceding Sui dynasty onward. Two-handed changdao ("long dao") or modao were also used in the Tang, with some units specializing in their use.

During the Song dynasty, one form of infantry dao was the shoudao, a chopping weapon with a clip point. While some illustrations show them as straight, the 11th century Song military encyclopedia the Wujing Zongyao depicts them with curved blades – possibly an influence from the steppe tribes of Central Asia, who would conquer parts of China during the Song period. Also dating from the Song are the falchion-like dadao, the long, two-handed zhanmadao, and the long-handled, similarly two-handed buzhandao (步戰刀).^{[citation needed]}