Castejón de Henares is a municipality in the province of Guadalajara, in the autonomous community of Castile-La Mancha, Spain. It is a small rural settlement in the central part of the country, within the comarca of the Alcarria region of Guadalajara.
The municipality is sparsely populated. According to the 2004 census carried out by the Instituto Nacional de Estadística (INE), Castejón de Henares had a population of 106 inhabitants. Its small size places it among the many minor municipalities that make up the largely rural interior of Guadalajara province.
As a municipality, Castejón de Henares forms part of the local administrative structure of Castile-La Mancha, with its own municipal government. Its name derives from the Spanish term for a fortified settlement and from the Henares river, which gives its name to the surrounding area.