Laysan is one of the Northwestern Hawaiian Islands, located 808 nautical miles northwest of Honolulu. It comprises one land mass of 1,016 acres (4.11 km2), about 1 by 1+1⁄2 miles in size. It is an atoll of sorts, although the land completely surrounds a shallow central lake some 2.4 m (7.9 ft) above sea level that has a salinity approximately three times greater than the ocean. Laysan's Hawaiian name, Kauō, means 'egg'.

The Northwestern Hawaiian Islands or Leeward Hawaiian Islands are a series of islands and atolls in the Hawaiian island chain located northwest of the islands of Kauai and Niʻihau. Politically, they are all part of Honolulu County in the U.S. state of Hawaii, except Midway Atoll, which is a territory distinct from the State of Hawaii, and grouped as one of the United States Minor Outlying Islands. The United States Census Bureau defines this area, except Midway, as Census Tract 114.98 of Honolulu County. Its total land area is 3.1075 square miles (8.048 km2). All the islands except Nihoa are north of the Tropic of Cancer, making them the only islands in Hawaii that lie outside the tropics.