Bassae (Latin) or Bassai, Vassai or Vasses (Greek, Modern: Βάσσες, Ancient: Βάσσαι), meaning "little vale in the rocks", is an archaeological site in the northeastern part of Messinia Prefecture that was a part of Arcadia in ancient times. Bassae lies near the village of Skliros, northeast of Figaleia, south of Andritsaina and west of Megalopolis. It is famous for the well-preserved mid- to late-5th century BCE Temple of Apollo Epicurius.

Although this temple is geographically remote from major polities of ancient Greece, it is one of the most studied ancient Greek temples because of its multitude of unusual features. Bassae was the first Greek site to be inscribed on the World Heritage List (1986). Its construction is placed between 450 BCE and 400 BCE.