Fuentelsaz is a municipality in the province of Guadalajara, within the autonomous community of Castile-La Mancha, Spain. It is located in the central-eastern part of the country, in the region historically known as Castile.
According to the 2004 census conducted by Spain's National Statistics Institute (INE), the municipality had a population of 118 inhabitants. This small population figure reflects the pattern of rural depopulation common to many municipalities in the Guadalajara province.
As a municipality, Fuentelsaz constitutes a basic unit of local administration in Spain, encompassing the settlement and its surrounding territory within the Guadalajara provincial framework.