Tawantinsuyu reached its greatest extent under Huayna Capac, as he expanded the empire's borders south along the Chilean coast, and north through what is now Ecuador and southern Colombia.

According to the priest Juan de Velasco he absorbed the Quito Confederation into his empire by marrying Queen Paccha Duchicela, halting a long protracted war.

[6][7][8] Huayna Capac's original name was Tito Cusi Huallpa (Hispanicized spelling) Tʼitu Kuši Wallpa (reconstructed Classical Quechua) before ascending to Sapa Inca.

[11] Subjects commonly approached Sapa Incas adding epithets and titles when addressing them, such as Wayna Qhapaq Inka Sapʼalla Tukuy Llaqta Uya "unique sovereign Huayna Capac, listener to all peoples".

[17]: 112 [1]: 112, 118 In addition to Kusi Rimay and Rawa Uqllu, Huayna Capac had more than 50 wives including Usika, Lari, Anawarqi, Kuntarwachu and Añas Qulqi.

In the Sacred Valley, the sparse remains of one of Huayna Capac's estates and his country palace called Kispiwanka[23] can still be found in the present-day town of Urubamba, Peru.

In what is now Bolivia, Huayna Capac was responsible for developing Cochabamba as an important agriculture and administrative center, with more than two thousand silos (qullqas) for corn storage built in the area.

[citation needed] Further north in Ecuador, Huayna Capac's forces attempted to expand into the lowlands of the Amazon basin, reaching the Chinchipe River, but they were pushed back by the Shuar.

[24] Huayna Capac acquired a special fondness for the central Peruvian Andes and its local highlights; he is recorded as having spent time relaxing in the Chinchaycocha lake on the Bombon plateau.

[25] On its way to Cusco, after Huayna Capac's death in Quito, the procession carrying his body stopped in the vicinity of Shawsha, a city in the central Peruvian Andes, acknowledging the fondness that he had felt for the region, and because the local inhabitants had been some of the most loyal to its causes.

Tawantinsuyu, or the Inca Empire, reached the height of its size and power under his rule, stretching over much of what is now Bolivia, Peru, Argentina, Chile, Ecuador, and southwestern Colombia.

The empire spanned 3,500 kilometres (2,200 mi) north to south, comprising the desert coast of Pacific Ocean on the west, the high Andes in the southeast and the forests of the Amazon Basin on the east.

[28]: 82–83, 85  When Huayna Capac returned to Quito he had already contracted a fever while campaigning in present-day Colombia (though some historians dispute this),[29] likely resulting from the introduction of European disease like measles or smallpox.

Atahualpa began securing support from Huayna Capac's best generals, Chalcuchíma and Quizquiz, who happened to be near Quito, the nearest major city.