Radiocarbon dating of charcoal from iron slag revealed evidence of continuous iron smelting in the Khasi Hills, Meghalaya, NE India spanning the last two millennia. The slag layer, which is dated to 2040 ± 80 years BP (353 BC-AD 128), is the earliest iron smelting site studied in the entire region of NE India. The presence of wüstite, fayalite, glass and metal iron, together with spinels such as hercynite in the slag, indicates that it was an acid product of a bloomery iron-making process. The relative isolation of the Khasi people, who inhabited a highly elevated plateau, is evidence of the indigenous origin of this manufacturing technology, although diffusion of knowledge through cultural and technical contacts or population migration cannot be excluded.