Chasseur, a French term for "hunter", is the designation given to certain regiments of French and Belgian light infantry or light cavalry to denote troops trained for rapid action.

Light infantry refers to certain types of lightly-equipped infantry throughout history. They have a more mobile or fluid function than other types of infantry, such as heavy infantry or line infantry. Historically, light infantry often fought as scouts, raiders, and skirmishers. These are loose formations that fight ahead of the main army to harass, delay, disrupt supply lines, engage the enemy's own skirmishing forces, and generally "soften up" an enemy before the main battle. Light infantrymen were also often responsible for screening the main body of a military formation.