Armuña de Tajuña is a municipality in the province of Guadalajara, in the autonomous community of Castile-La Mancha, Spain. It lies in the central part of the country, within the comarca traditionally associated with the Tajuña river valley, from which the settlement takes the second part of its name.
The municipality is small and rural. According to the 2004 census carried out by the Instituto Nacional de Estadística (INE), Armuña de Tajuña had a population of 122 inhabitants. That figure reflects the pattern common to many villages in the sparsely populated interior of Guadalajara province.
Its administrative status is that of a municipality, the basic unit of local government in Spain, and its official census records are maintained by the INE. Beyond its location in the province of Guadalajara and its recorded population, few details about the village are documented in the available source material.