Navajo County is in the northern part of the U.S. state of Arizona. As of the 2020 census, its population was 106,717. The county seat is Holbrook.

Navajo County contains parts of the Hopi Indian reservation, the Navajo Nation, and Fort Apache Indian Reservation.

Navajo County was split from Apache County on March 21, 1895. The first county sheriff was Commodore Perry Owens, a legendary gunman who had previously served as the sheriff of Apache County. It was the location for many of the events of the Pleasant Valley War.