Abajas is a municipality and town in the province of Burgos, within the autonomous community of Castile and León, Spain. It is located in the northern part of the country, in the region historically known as Old Castile.
The municipality is small and sparsely populated. According to the 2004 census conducted by Spain's National Statistics Institute (INE), Abajas had a population of 41 inhabitants. The town and the municipality share the same name, as is common in this part of Spain, where the municipal territory typically includes the main settlement and surrounding rural land.
Like many municipalities in rural Burgos, Abajas is characterized by its small size and low population density, reflecting the broader demographic pattern of depopulation seen across much of inland Castile and León during the twentieth century.