Kure Atoll or Ocean Island is an atoll in the Pacific Ocean 48 nautical miles west-northwest of Midway Atoll in the Northwestern Hawaiian Islands at 28°25′N 178°20′W. A coral ring 10 km across encloses a lagoon several meters deep. The only land of significant size is called Green Island and is a habitat for hundreds of thousands of seabirds. A short, unused and unmaintained runway and a portion of one building, both from a former United States Coast Guard LORAN station, are located on the island. Politically, it is part of Hawaii, although separated from the rest of the state by Midway, which is a separate unorganized territory. Green Island, in addition to being the nesting grounds for tens of thousands of seabirds, has recorded several vagrant terrestrial birds, including snow bunting, eyebrowed thrush, brambling, olive-backed pipit, black kite, Steller's sea eagle and Chinese sparrowhawk. It is currently managed as a Wildlife Bird Sanctuary by the State of Hawaii's Department of Land and Natural Resource–Division of Forestry and Wildlife as one of the co-trustees of Papahānaumokuākea Marine National Monument with support from the Kure Atoll Conservancy.

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.