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 (48,300 km2), or 16.4% of Arizona's total area, and is larger than the nine smallest states in the U.S.

Grand Canyon National Park, located in northwestern Arizona, is the 15th site in the United States to have been named as a national park. The park's central feature is the Grand Canyon, a gorge of the Colorado River, which is often considered one of the Wonders of the World. The park, which covers 1,217,262 acres of unincorporated area in Coconino and Mohave counties, received more than 4.7 million recreational visitors in 2023. The Grand Canyon was designated a World Heritage Site by UNESCO in 1979. The park celebrated its 100th anniversary on February 26, 2019.