Religion in Yap is predominantly Roman Catholic, which first arrived in Yap in the late 1880s. Before that, the Yapese people practiced traditional rituals and practices and held beliefs about the gods, the spirits, taboos, and death. Through the efforts of Capuchin and Jesuit missionaries, the Catholic Church eventually became the dominant church on Yap. Other religions on Yap include Protestantism and other Christian sects.

Yapese mythology shares many commonalities with Chuukic mythology, though the direction of diffusion is unknown.

The Yapese creation myth starts with the god Gavur li yel yel creating the four layers of cosmos, the dark unnamed tier where Gavur li yel yel resides, the sky layer, the earth, and the underworld beneath the sea. He used his hands and dirt to create the chief god Yanolop, who in turn used his mind (mam) to create five other sky deities, four male and one female. The female deity, Matsugulop, mates with the male deities and they create another generation of sky gods. Different accounts credit Gavur li yel yel or Yanolop for creating Solal, the god of the world-under-the-sea. Gavur li yel yel then creates five gods of the world-under-the-sea, four male and one female. Like the first generation of sky gods, the gods of the world-under-the-sea marry and inter-marry to create new generations of gods.

Yälfaath the Elder, a member of the first generation of sky gods, is regarded as the creator of the human race. He used his hands and dirt to create the first man and woman, named Ganan and Nik. He created another couple using the same method the next day, but then decided it would be faster to give the humans sexual organs to allow them to reproduce by themselves.

Traditional Yapese belief holds that each living person has two souls; one that lives (yaan ni fos) and one that dies (yaan ni yam). At death, the soul-that-lives wanders the earth while the soul-that-dies gets eaten by the sky god Lug and a friend. A ritual prayer and incantation (ma’log) induces the soul to a place called Gatsam where it can stay or go to heaven.

Those who choose to go to heaven must first offer money to the guard Rumang and pass his judgment. They then enter into Yanolop's clubhouse, where Yanolop separates the spirits he considers "bad" (for example, those with disease, or women who die during childbirth) from those he considers "good". People of different classes go to different places in heaven. For example, the souls of warriors who die in battle, women who die during childbirth, and fishermen who die at sea all go to their own places in the afterlife.

The initiation into eating ranks in the district of Rull starts with the lunar month Monyibwuo. The next month, Wagaeygaey, the Yapese prepare by planting yam gardens. People from Rull spend the next month Tafgif cleaning their yards and graves. They also place food offerings on graves, which is later eaten by people of Gitam. Makan is a sacred month on Yap which starts with the disappearance of the constellation Pleiades. Eating class initiates spend this time in fasting, seclusion, and learning. The priests of Pemgoy and Alog gather at a shrine of Rull. For the month's last ten days, a magician divines for the eating class and its initiates by burning bundles of material. On the last month of this calendar, Rir, the initiates are welcomed as new members of the eating class. They then prepare a feast for visitors of the district who come from southern Yap.

Traditional Yapese religious beliefs emphasize a ritual of taboo which includes eating practices, female seclusion, and death customs.