Stenberga Castle (also known as Teinperi) was a small medieval castle in Masku, Finland. It was originally built of gray stone, consisting of two towers with outer dimensions of 13 by 13 metres (43 by 43 ft) and 9 by 7 metres (30 by 23 ft), respectively. The castle walls were 2 metres (7 ft) thick. In a later phase, bricks were also used in the construction. The castle was on a steep rock, presumably an island back then, by the sea near the mouth of Hirvijoki River, flowing from Nousiainen. Due to the post-glacial rebound, the location is now almost 2 kilometres (1.2 mi) from the coastline. Very little remains of the castle.