Meṣad Hashavyahu is an ancient fortress on the border of ancient Judea facing the Philistine city of Ashdod near the Mediterranean Sea. It lies 1.7 km south of Yavne-Yam (the seaport) and 7 km northwest of Yavne (the main city). The original name of the fort is unknown, but was given the name found on several inscribed pottery shards (ostraca) recovered at the site.