Atarjea is a city and municipality situated in the easternmost region of the Mexican state of Guanajuato. It is located within the Sierra Gorda mountain range and covers a total land area of 318 square kilometres.
The municipality shares borders with several neighboring regions, including the state of San Luis Potosí to the north, the state of Querétaro to the east and south, and the municipality of Xichú to the west. According to the 2005 census, Atarjea had a recorded population of 5,198 residents.