Sepoy, related to sipahi, is a term denoting professional Indian infantryman, traditionally armed with a musket, in the armies of the Mughal Empire and the Maratha Army.

The sipahi were professional cavalrymen deployed by the Seljuk Turks and later by the Ottoman Empire. Sipahi units included the land grant–holding (timar) provincial timarli sipahi, which constituted most of the army, and the salaried regular kapikulu sipahi, or palace troops. However, the irregular light cavalry akıncı ("raiders") were not considered to be sipahi. The sipahi formed their own distinctive social classes and were rivals to the janissaries, the elite infantry corps of the sultans.