- Before the coming of the Castilians, the religion of the people of Tawantinsuyu was polytheistic in nature. Wiraqucha created the earth, stars, and all living things. He created the moon and the sun by plucking them from an island in Lake Titicaca.
- Inti, was the god of the sun. The Sapa Inca was the "Son of the Sun", a direct descendant of the sun god, and when he died he returned to the sun. The largest Inca religious event each year was the nine-day Inti Raymi festival, held on the winter solstice, which, in the southern hemisphere, is in June.
- Another important god was Illapa, the god of rain, thunder, lightning, and war.
- Mama Killa was the moon god and sister-wife to Inti. The Incans believed that she shed tears of silver, and during lunar eclipses she was believed to have been swallowed up by a puma. The Incas pounded their drums and blew horns so that they could stop the eclipse.
- In addition, the Incas also worshiped their gods in spiritual places called wak'as. These wak'as could be caves, springs, oddly shaped rocks, and man-made shrines. Battlegrounds and cemeteries were also considered wak'as.
- The main shrine in Quzqu was called the Qurikancha, the interior of which was decorated in silver and gold. It contained six buildings which were set aside for the worship of the six main gods. Within this temple were wall niches in which the bodies of previous Sapa Inkas were exhibited along with various statues of Inti in certain festivals. Some figures of Inti also depicted him in human form with a hollowed out midsection that was filled with a concoction made of gold dust and the ashes of the Incas' hearts.
- Throughout the Empire large quantities of natural and human resources were set aside for Inti. Each conquered province was supposed to dedicate a third of their lands and herds to Inti. Each major province would also have a Sun Temple in which male and female priests would serve. The female priests were the mamakuna, who were chosen from the aqllakuna ("chosen women"), and they would weave special cloth and brew chicha for festivities and sacrifices to Inti.
- The head priest of the Inca religion was called the uma uillaka. Under them were the administrative priests, the hatun uillcas. The local priests were called yana uillakas. The priests would teach the people about the gods, hear confessions, and assign a penance for their sins.
- Animals were sacrificed daily. Human sacrifice was rare and only occurred when the sacrificing of animals did not appear to be sufficient.
- The entire month of November was Ayamarka, the "Festival of the Dead". It was celebrated with wailing, funeral singing and professional mourners. It was the custom to visit the graves of ancestors, leaving them gifts of food and drink.
- Inti is represented as a golden disk with rays and a human face. These disks were displayed in the Qurikancha and in temples throughout the Empire. This representation, adorned with ear spools, a pectoral, and a royal headband, was known as a punchao (Quechua for "day").
- Just as there are three diurnal stages of the sun, rising, noon and setting, so Inti's identity is also divided into three primary aspects: father, son, and brother. The first aspect is Apu Inti (Supreme Inti) who represents the father. He is known as "The Lord Sun". He is associated with the summer solstice. The second aspect is Churi Inti (Son Inti) who represents the son of Inti and is known as "Daylight." He is associated with the winter solstice. The third aspect is Inti Wawqi (Inti brother). Inti Wawqi also represents Inti in his specific position as the founding father of the Inka Empire and the center of the state's official religion.
- The festival of Inti Raymi honoring the sun god was originally meant to celebrate the start of a new planting season. The name of the festival, Inti Raymi, is translated as "sun festival". It was celebrated during the Southern Hemisphere's winter solstice, the shortest day of the year, falling at the end of June.
- This festival was attended by the four sectors of Tawantinsuyu. Military captains, government officials, and the vassals who attended were dressed in their best costumes and carried their best weapons and instruments.
- Preparation for the festival began with a fast of three days, during which no fire was lit and the people refrained from having sexual intercourse. This festival would last for nine days, and during this time the people consumed massive amounts of food and drink. There were many sacrifices as well, which were all performed on the first day. After the nine days everyone would leave with the permission of the Sapa Inka.
- With the arrival of Christianity, Inca worship began to evolve under its influence. Inti is now understood to be the only god. The other gods are revered as manifestations of the one god.
- The Qurikancha remains the main temple of Inti worship. The word Qurikancha is used, by way of synecdoche, to mean the office of the uma uillaka (cf. the Vatican, the White House).
- Smaller temples are erected in the cities and villages for communal worship. Private devotions still take place at wak'as.
- The uma uillaka remains the head of the religion. The office of hatun uillaka has evolved from providing adminstrative service (carried out now by laypeople) into the head priest of each suyu. Thus, there are four of them. The yana uillcas continue to serve the local communities as leaders of weekly worship. They also officiate at initiation ceremonies, weddings and funerals. The office of uillaka is open to both men and women. The uillakas are paid by the government.
- Animal sacrifices no longer take place. Instead, a commercial unfermented maize chicha morada is served as a sacrament. It must be made solely of maize with no other additives. In smaller communities, the chicha may be made by the local people.
- A golden Inti symbol is placed prominently in every temple.
- Coincidentally the Catholic celebration of All Souls' Day on November 2 occurs in the month of the Ayamarka. Ayamarka is now celebrated on the first Sunday of November. The people still visit the graves of their family members on which they pour a libation of chicha.
- As the Inkas before the arrival of the Castilians did not have weeks, the uillakas decided to observe Sundays as the Inti day of worship, so as not to disturb the flow of the seven-day week introduced by the Castilians.
- The festival of Inti Raymi is still celebrated. However, it has evolved into more than a religious celebration. It has taken on the aspect of a carnival, rather like Mardi Gras.
- Since the restoration of the Empire in 1780 in the person of Tupaq Amaru II, the 21st Sapa Inka, the cremated bodies of deceased Sapa Inkas are buried in a mausoleum in Macchu Picchu.
- Under the influence of Catholic theology the threefold aspects of Inti have taken on a trinitarian nuance. Apu Inti (Supreme Inti), the father is believed to be analogous to the First Person, God the Father. Churi Inti (Son Inti) the son of Inti is believed to be analogous, not to the Son of God, the Second Person, but to the Holy Spirit, the Third Person. He is the Daylight that moves and inspires humans. Therefore, Inti Wawqi (Inti brother) is believed to be analogous to the the Son of God, the Second Person, who, as the founder of the Empire is manifested, not incarnated, in the Sapa Inka.