Papahānaumokuākea Marine National Monument, Marine national monument in the Northwestern Hawaiian Islands, United States

Papahānaumokuākea Marine National Monument protects 582,578 square miles (1.5 million km²) of Pacific Ocean, including ten islands and atolls of the Northwestern Hawaiian Islands, more than 30 submerged banks and seamounts, and coral reefs. Its boundary runs from offshore of Nīhoa 1,200 miles northwest to Kure Atoll and crosses the International Date Line. Only 5.8 square miles (15 km²) of land lies above sea level.

President Theodore Roosevelt created the Hawaiian Islands Bird Reservation in 1909 to stop seabird over-harvesting. Franklin D. Roosevelt made it the Hawaiian Islands National Wildlife Refuge in 1940. Bill Clinton established the Northwestern Hawaiian Islands Coral Reef Ecosystem Reserve in 2000. George W. Bush proclaimed the national monument on 15 June 2006, and UNESCO listed it as a World Heritage Site in 2010.

Native Hawaiians consider the Northwestern Hawaiian Islands the place where life begins and to which spirits return after death, a kinship between nature and humanity. Archaeological remains on Nihoa and Mokumanamana show settlements from before contact with Europeans. The monument's Hawaiian name was given on 2 March 2007, replacing the earlier Northwestern Hawaiian Islands Marine National Monument.

Access requires special permits because the area remains strictly protected and open only for scientific research and Native Hawaiian traditional practices. The Mokupāpapa Discovery Center in Hilo offers visitors exhibits and educational programs about the reserve and its inhabitants.

The monument's boundary crosses the International Date Line past Kure Atoll, so its protected waters are continuous across the antimeridian. Midway Atoll, part of the United States Minor Outlying Islands rather than the state of Hawaii, holds Henderson Field, the public airport that provides access to the monument.