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 x 13 and 9 x 7 metres, respectively. The castle walls were two metres thick. In a later phase, bricks were also used in the construction. The castle was situated 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 km from the coastline.