Vanaja is a former municipality of Finland. It was located in Tavastia Proper about 100 kilometres (60 mi) north of Helsinki. It is also speculated that it might have been the name for an Iron Age and early Middle Ages settlement found opposite to the Häme Castle. The medieval church of Vanaja is located about 3 km (2 mi) south-east of the Iron Age settlement, on a cape, that may have served as the local place of sacrifice. The oldest Swedish name (Vaan-ö) of the municipality probably originated from the name of the cape, which during springtime floods used to be an island. There was an episcopal manor nearby in the 14th and 15th century.
According to preliminary estimations, the site was about 5.5 hectares (14 acres) hectares making it about half the size of the Björkö settlement in Sweden. Excavations have so far covered only a small fraction of the area, and its nature as a town-like settlement or just an ordinary rural site has been disputed. The site was found in 1986.