Kapingamarangi is an atoll and a municipality in the state of Pohnpei of the Federated States of Micronesia. It is by far the most southerly atoll or island of the country and the Caroline Islands, 300 km (190 mi) south of the next southerly atoll, Nukuoro, and 740 km (460 mi) southwest of the main island of Pohnpei state; it forms a Polynesian outlier.

An atoll is a ring-shaped island, including a coral rim that encircles a lagoon. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical parts of the oceans and seas where corals can develop. Most of the approximately 440 atolls in the world are in the Pacific Ocean.