相模湾（さがみわん）是位于日本关东地方南部的一个海湾。范围为三浦半岛南端城岛（三浦市）到真鹤半岛真鹤岬（真鹤町）之间连接以北的海域。相模湾是北美板块与菲律宾海板块交界地，三次关东大地震的震源——相模断层通过这里，湾内最深处达1600米。

Sagami Bay(相模湾,Sagami-wan, also known as the Sagami Gulf or Sagami Sea) lies south of Kanagawa Prefecture in Honshu, central Japan, contained within the scope of the Miura Peninsula, in Kanagawa, to the east, the Izu Peninsula, in Shizuoka Prefecture, to the west, and the Shōnan coastline to the north, while the island of Izu Ōshima marks the southern extent of the bay. It lies approximately 40 kilometres (25 mi) southwest of the capital, Tokyo. Cities on the bay include Odawara, Chigasaki, Fujisawa, Hiratsuka, Itō, and Kamakura.