Old Castle of Lieto (Finnish: Liedon Vanhalinna) is a formerly fortified hill in Lieto, Finland. The original name of the castle is not known. According to excavations, the castle has been in use in the Late Bronze Age (1500–500 BCE), in Middle Iron Age (500–700 CE, contested) and in the Middle Ages up to the end of the 14th century, when it was replaced by the "new castle" in Turku harbour. It probably served as the first Swedish fortress in Finland from the mid-13th century onwards after the Second Swedish Crusade. Constructions on the hilltop were mostly of wood.