Coconino County is a county in the north-central part of the U.S. state of Arizona. Its population was 145,101 at the 2020 census. The county seat is Flagstaff. The county takes its name from Cohonino, a name applied to the Havasupai people. It is the second-largest county by area in the contiguous United States, behind San Bernardino County, California. It has 18,661 sq mi, or 16.4% of Arizona's total area, and is larger than the nine smallest states in the U.S. Coconino County comprises the Flagstaff metropolitan statistical area, Grand Canyon National Park, the federally recognized Havasupai Nation, and parts of the federally recognized Navajo, Hualapai, and Hopi nations.