Apache County is in northeastern Arizona with New Mexico to the east and Utah to the north. Apache County consists of 11,205 square miles of land and 14 square miles of water, making Apache County the 6th largest county in the 48 contiguous states.

Canyon de Chelly is completely contained in Apache County. Parts of Petrified Forest National Park and the Navajo and Fort Apache Indian Reservations are also in Apache County. The county seat is St. Johns.