A grenadier ( GREN-ə-DEER, French: [ɡʁənadje] (listen); derived from the word grenade) was originally a specialist soldier who threw hand grenades in battle. The distinct combat function of the grenadier was established in the mid-17th century, when grenadiers were recruited from among the strongest and largest soldiers. By the 18th century, the grenadier dedicated to throwing hand grenades had become a less necessary specialist, yet in battle, the grenadiers were the physically robust soldiers who led assaults, such as storming fortifications in the course of siege warfare.

Certain countries such as France (Grenadiers à Cheval de la Garde Impériale) and Argentina (Regiment of Mounted Grenadiers) established units of Horse Grenadiers and for a time the British Army had Horse Grenadier Guards. Like their infantry grenadier counterparts, these horse-mounted soldiers were chosen for their size and strength (heavy cavalry).

Today, the term is also used to describe a soldier armed with a grenade launcher, a weapon that fires a specially designed large-caliber projectile, often with an explosive, smoke, or gas warhead. These soldiers operate as part of a fireteam.