Palmyra Atoll (), also referred to as Palmyra Island, is one of the Northern Line Islands (southeast of Kingman Reef and north of Kiribati). It is located almost due south of the Hawaiian Islands, roughly one-third of the way between Hawaii and American Samoa. North America is about 3,300 miles (5,300 kilometers) northeast and New Zealand the same distance southwest, placing the atoll at the approximate center of the Pacific Ocean. The land area is 4.6 sq mi (12 km²), with about 9 miles (14 km) of sea-facing coastline and reef. There is one boat anchorage known as West Lagoon, accessible from the sea by a narrow artificial channel.

It is the second-to-northernmost of the Line Islands, and one of three American islands in the archipelago, along with Jarvis Island and Kingman Reef. Palmyra Atoll is part of the Pacific Remote Islands Marine National Monument, the world's largest marine protected area. The atoll comprises submerged sand flats along with dry land and reefs. It comprises three lagoons separated by coral reefs. The western reef terrace is one of the biggest shelf-reefs, with dimensions of 2 by 3 miles (3.2 by 4.8 km). Over 150 species of coral inhabit Palmyra Atoll, double the number recorded in Hawaii.

Palmyra Atoll has no permanent population. It is administered as an incorporated unorganized territory, presently the only one of its kind, by the U.S. Fish and Wildlife Service of the U.S. Department of the Interior. The territory hosts a variable transient population of 4–25 staff and scientists employed by various departments of the U.S. government and by The Nature Conservancy, as well as a rotating mix of Palmyra Atoll Research Consortium scholars. Submerged portions of the atoll are administered by the Department of the Interior's Office of Insular Affairs.