Atarjea is a Mexican city (and municipality) located in the easternmost region of the state of Guanajuato, within the Sierra Gorda range. The municipality has an area of 318 square kilometres (1.04% of the surface of the state) and is bordered to the north by the state of San Luis Potosí, to the east and south by the state of Querétaro, and to the west by Xichú.