The Federated States of Micronesia is overwhelmingly Christian, split between a Catholic majority, especially strong in Chuuk and Pohnpei, and Protestant communities, particularly a Congregationalist tradition descended from nineteenth-century American Board missionaries, strongest in Kosrae and parts of Pohnpei, together accounting for the great majority of the population per estimates reflected in Pew Research's Religious Composition of the World, 2010-2020.
Pre-Christian Micronesian religious practice varied considerably across the four states' distinct island cultures but generally centered on ancestor veneration, nature and clan spirits, and specialist ritual practitioners overseeing navigation, healing and agricultural fertility rites, and Pohnpei's Nan Madol, a monumental complex of artificial islets built from massive basalt columns beginning around the twelfth century CE, served as both the political capital and the religious and ceremonial center of the Saudeleur dynasty, a site local oral tradition surrounds with continuing spiritual reverence and caution regarding its ruins.
Spanish, German and Japanese colonial administrations from the late nineteenth century through the Second World War each brought their own missionary activity, chiefly Catholic under Spanish and German rule, before American Protestant missionary influence expanded significantly under the postwar United States-administered Trust Territory of the Pacific Islands.