Junkarsborg was a medieval castle in Karis, Raseborg, Finland. Today, only rectangular earth walls remain. Archaeologists suppose that the castle was built in the early 14th century and was used until the beginning of the 15th. It probably was a predecessor of the Castle of Raseborg only a few kilometers away. Some coins from late 14th century have been found. The site has been excavated 1891–92, 1937, and 1950–54.