The Mansion Site in Seongdong-dong, Gyeongju () is an archaeological site in Seongdong-dong, Gyeongju, South Korea. On January 21, 1963, it was designated a Historic Site of South Korea.
The site was first discovered during a public works project in 1937. It is believed to be a site of a complex of buildings from the Unified Silla period that possibly belonged to the local government or a noble. Various relics, including tiles and bowls, have been recovered from the site.