Langreo (Spanish pronunciation:[laŋ.ˈgɾe.o]; Asturian:Llangréu) is a municipality and town of northern Spain, province of The Principality of Asturias. It is the 4th largest town of Asturias with 43.000 inhabitants. Langreo is located in the centre of Asturias, approximately 20km of Oviedo. It was an important mining and metallurgical center.