The Inca army (Quechua: Inka Awqaqkuna) was the multi-ethnic armed forces used by the Tawantin Suyu to expand its empire and defend the sovereignty of the Sapa Inca in its territory.

Thanks to the military mit'a, as the empire grew in size and population, so did the army, reaching 200,000 men in a single army (during the reign of Huayna Capac). The soldiers were provided with food, clothing and state aid in replacing their family in regard to the agrarian activity that the recruited should be fulfilling, in such a way that being a permanent soldier was not a bad position and even occupied its own space in the political-social pyramid.

During the Manco Inca rebellion, the soldiers used Spanish weapons and armor, and learned how to ride horses. After the retreat to Vilcabamba, they began to use guerrilla tactics against the Viceroyalty of Peru. The Inca army was finally dissolved after the death of the last Inca of Vilcabamba, Tupac Amaru I, in 1572.

As the Inca Empire grew, an army created by a loose confederation of peasant warriors was replaced by one of professional officers. These officers were chosen during the Warachikuy festival, during which candidates had to undergo various tests of physical skill: such as racing, marksmanship, simulated combat and to see if they could stay awake for a long period, with it being reported that some officers could remain awake for a whole week.

Inca battalions contained permanent staff (generals and officers) and non-permanent personnel composed of drafted hatun runas (common men), who would be serving their military mit'a public service, comparable to mandatory military service or the draft. Once the mit'a was fulfilled, each hatun runa would return to their respective ayllu (community).

Each battalion was made up of a single ethnic group, the whole group being directed by a kuraka (warlord) of the same ethnicity. In the event that a kuraka fell in battle, a replacement was appointed from within the same ethnic group. To prevent rebellions and to promote successful performance in battle, two battalions were formed per ethnic group, each one under the command of a general (and both under the command of the kuraka). Promotion was given to the general who gave the greatest display of bravery on the battlefield, which led to competition between the two battalions. This concept of "duality" is widespread in the Andean world and represents the two Inca dynasties: Hanan and Hurin.

From the time of the rule of Emperor Tupac Yupanqui, a specialized elite group of soldiers was appointed for the safekeeping of the Sapa Inca ("the one and only Inca") during parades, travel or campaigns. These bodyguards originated primarily in Cusco, though soldiers from other ethnicities were also accepted in their ranks. This imperial guard, consisting entirely of men belonging to the nobility, reached a size of 10,000 warriors.

All members of the Inca Army were between 25 and 50 years old. All of the empire's citizens had to perform either military or community service. One in every 50 men over 25-years-old (the legal age of responsibility in the Inca Empire) would be chosen for military service. For noblemen, this was an honour and a duty, for common men, it was a means of social promotion. In accordance with the duality concept, one of every 50 young women was selected to serve in the Temple of the Virgins of the Sun.