Thoas may refer to several figures in Greek mythology:

• Thoas (king of Lemnos), saved by his daughter Hypsipyle from the massacre by the Lemnian women, a son of Dionysus and Ariadne, sometimes identified with Thoas (king of the Taurians) below
• Thoas (king of the Taurians), king when Iphigenia became priestess of Artimis, sometimes identified with Thoas (king of Lemnos) above
• Thoas (king of Aetolia), a Greek hero and leader in the Trojan War, son of Andraemon and Gorge
• Thoas (king of Corinth), a son of Ornytion and a grandson of Sisyphus
• Thoas (son of Jason and Hypsipyle), a son of Jason, the leader of the Argonauts, and Hypsipyle the daughter of Thoas, the king of Lemnos (above), and the brother of Euneus
• Thoas (mythology), other figures named "Thoas" in Greek mythology

Thoas may also refer to:

• 4834 Thoas, an asteroid named after the Greek mythological Trojan War hero
• An ancient name of the Achelous River