Cuirassiers (; from French cuirassier [kɥiʁasje]) were cavalry equipped with a cuirass, sword, and pistols. Cuirassiers first appeared in mid-to-late 16th century Europe as a result of armoured cavalry, such as men-at-arms and demi-lancers, discarding their lances and adopting the use of pistols as their primary weapon. In the later part of the 17th century the cuirassier lost his limb armour and subsequently wore only the cuirass (breastplate and backplate), and sometimes a helmet. By this time, the sword or sabre had become his primary weapon, with pistols relegated to a secondary function.

Cuirassiers achieved increased prominence during the Napoleonic Wars and were last fielded in the opening stages of World War I (1914-1918). A number of countries continue to use cuirassiers as ceremonial troops.

The French term cuirassier means "one with a cuirass" (French: cuirasse), the breastplate armour which they wore.