Cantonists (Russian: кантонисты; more properly: военные кантонисты, "military cantonists") were underage sons of conscripts in the Russian Empire. From 1721 on they were educated in special "cantonist schools" (Кантонистские школы) for future military service (the schools were called garrison schools in the 18th century). The cantonist schools and the cantonist system were eventually abolished in 1857, following public and international criticism and the Russian defeat in the Crimean War.

Cantonist schools were established by the 1721 Tsar Peter the Great's decree, which stipulated that every regiment was required to maintain a school for 50 boys. Their enrollment was increased in 1732, and the term was set from 7 to 15. The curriculum included grammar and arithmetic, and those with a corresponding aptitude were taught artillery, fortification, music and singing, scrivenery, equine veterinary science, or mechanics. Those lacking such talents were taught carpentry, blacksmithing, shoemaking, and other trades applicable to the military. The most able were trained for a further three years, until 18. All entered military service after their studies. The decree of 1758 required all male children of the military personnel to be taught in the cantonist schools. In 1798, a military "asylum orphanage" was established in Saint Petersburg, and all regimental schools were renamed after it, the total enrollment reaching 16,400.

The schools were reorganized in 1805, and all children were now referred to as cantonists. Their number increased dramatically after the French invasion of Russia in 1812, when many orphaned sons of military personnel killed in the war enrolled in canton schools voluntarily. During this period, the curriculum was equivalent to that of gymnasia and military subjects were not taught.

In 1824, all canton schools were made answerable to the Director of Military Settlements, Count Aleksey Arakcheyev, and in 1826, they were organized into canton battalions. Curriculum standards dropped significantly, and subjects were limited to those applicable to the military.

During the reign of Nicholas I of Russia, cantonists reached 36,000. Several canton battalions became specialized: they prepared auditors, artillerists, engineers, military surgeons, and cartographers.

More boys were added to the category of cantonists. Eventually, sons of discharged soldiers, illegitimate sons of soldiers' partners or widows, and even foundlings were included.

There were several exemptions:

There were considerable differences in cantonists' service obligations: