According to the myths Thoas was one of the sons of the wine-god Dionysus and his wife Ariadne. Thoas' brothers were Oenopion, Staphylus, Latramys, Euanthes and Tauropolus. Sometimes it was said that Thoas' father was Theseus, perhaps not only due to the reason that Thoas' mother Ariadne and Theseus were lovers, but also because Thoas' kingdom was under the control of the Athenians.
All of the children of Dionysus became the founders of the Hellenic tribes on various places in the Aegean, where the non-Greek inhabitants were living. Thoas, who received from his uncle Rhadamanthys the island of Lemnos (situated in the northern part of the Aegean Sea) became the king of this island.
However, after some time Thoas lost his throne when the women of the island revolted against their unfaithful husbands. According to a well-known story the Lemnian men complained about the fact that their spouses were foul-smelling and so they neglected their wives and took concubines from Thrace. This action made their spouses so angry, that these decided to eradicate the entire masculine population from Lemnos. Thereafter the queen of Lemnos became Hypsipyle, the daughter of Thoas. She saved her old father from a certain death by putting him secretly on a boat without sculls.
After dwelling on the sea for a while, Thoas arrived on the shores of the rocky island of Sicinos (Cyclades). He did not stay on this deserted place and traveled again back north. Later he finally arrived at Tauris (present-day Crym) and became its king. On this island, the goddess Artemis Tauris was also worshiped with the surname Thoantheia.
One of Thoas' grandsons, who were twins from his daughter Hypsipyle and Jason, was originally named Nebrophon but was also called Thoas the Younger.
The name Thoas is derived from the old Greek word thoazo, which means "to move quickly, to hurry up or to hasten." This name is a perfect fit for some of the situations in which this king of Lemnos appeared, especially when he had to move quickly or hurry from one place to another. This mythical story is connected with some specific historical events which happened when the first Greek colonists came to the island of Lemnos (where the old pre-Hellenic culture existed similar to the one in Troy) in about 800 BCE.
The name Thoas was relatively common and in the Greek myths more personages with this name can be found. One of them was a certain Thoas, Andraemonís son, and mentioned by Homer. He was the leader of the Aetolians who came with forty black ships to fight at Troy. The story goes that the famous hero Odysseus in his old age married Thoas' daughter.
Among the Trojans there existed another Thoas as well, who was killed during a fight with king Menelaus from Sparta.
Thoas was also one of three Athenian brothers who took a part in the expedition that Theseus made to the land of the Amazons. Pausanias also mentioned another Thoas, who was a younger son of Ornytion and the grandson of Sisyphus. Finally this author made an allusion to a giant named Thoas, who was killed in Arcadia.