Alaejos is a municipality in Spain, located in the province of Valladolid within the autonomous community of Castile and León. It lies in the northern part of the country, in the region traditionally known as the Tierra de Campos.
According to the 2011 census conducted by Spain's National Statistics Institute (INE), the municipality had a population of 1,467 inhabitants. As with many small municipalities in rural Castile and León, Alaejos is a compact settlement surrounded by open agricultural countryside.
Alaejos is one of numerous small municipalities that make up the province of Valladolid, a province whose capital is the city of Valladolid. The municipality's official population figures are recorded and published by the INE as part of Spain's national census system.