In Greek mythology, Eioneus (Ancient Greek Ἠιονεύς) is the Thracian father of Rhesus, the king who comes to Troy with horses "whiter than snow and swift as the winds" in Homer's Doloneia. He is the presumed eponym of the Thracian city of Eion; one later notice identifies him with the river-god Strymon, more commonly named as Rhesus' father.
Adapted from Wikipedia, "Eioneus" · CC BY-SA 4.0
I.Father of Rhesus
Homer (Iliad 10.435) makes Eioneus the father of Rhesus when Dolon describes the newly arrived Thracian king and his peerless horses to Odysseus and Diomedes. The patronymic anchors Rhesus in a Thracian coastal genealogy tied to the city of Eion on the Strymon.
Conon and related mythographers sometimes equate this Eioneus with Strymon himself, folding the mortal patronym into the river-god who is elsewhere Rhesus' father — a fork the atlas keeps as prose rather than a second node.
II.Homonyms
This atlas entry (eioneus-thrace) is the Thracian father of Rhesus. Distinct from Eioneus (or Deioneus) the Perrhaebian father of Dia, whose death at Ixion's hands is a separate Thessalian tale; from Eioneus son of Magnes, a suitor of Hippodamia slain by Oenomaus; from Eioneus son of Proteus in a Phrygian genealogy of Hecuba; and from Greek or Trojan warriors of that name killed in the Iliad and later epic.