Rhesus (/ˈriːsəs/; Ancient Greek: Ῥῆσος Rhêsos) is a mythical king of Thrace in The Iliad who fought on the side of Trojans.

According to Homer, his father was Eioneus who may be connected to the historic Eion in western Thrace, at the mouth of the Strymon, and the port of the later Amphipolis.

Later writers provide Rhesus with a more exotic parentage, claiming that his mother was one of the Muses[3] (Euterpe,[4] Calliope[5] or Terpsichore[6]) and his father, the river god Strymon.

Dolon explained that Rhesus had the finest horses, as well as huge, golden armor that was suitable for gods rather than mortals.

[11] Rhesus is also named as one of the eight rivers that Poseidon raged from Mount Ida to the sea in order to knock down the wall that the Achaeans built.