In Greek mythology, Ancaeus (Ancient Greek Ἀγκαῖος) is king of Samos, son of Poseidon and Astypalaea (or Althaea in variants), and an Argonaut famed for helmsmanship. He takes the Argo's helm after Tiphys dies and is the hero of the proverb "many a slip between the cup and the lip" when a boar kills him before he tastes his new vineyard's wine. Distinct from Ancaeus of Arcadia, the Calydonian boar-hunter.
Adapted from Wikipedia, "Ancaeus (son of Poseidon)" · CC BY-SA 4.0
I.Samian Argonaut
Apollonius pairs him with Erginus of Miletus as Poseidon's sons aboard the Argo; he leaves Parthenia, seat of Imbrasian Hera, boasting skill in seacraft and war. When Tiphys dies among the Mariandyni, Hera kindles courage in Ancaeus son of Astypalaea; he steers onward through the Clashing Rocks to Colchis.
Pausanias records a Samian house-epic of Asios: Ancaeus marries Samia daughter of Maeander and fathers Perilaus, Enudus, Samus, Alitherses, and Parthenope. Other strands make Altes the Lelegian his father.
II.Cup and lip
A seer warns that Ancaeus will never taste the wine of a vineyard he plants. Returning safely from the Argo, he raises a cup to mock the prophecy; the seer replies that much lies between cup and lip. An alarm of a boar in the vines draws him out — and the boar kills him before he drinks.
The atlas id ancaeus-samos is this Samian helmsman. Arcadian Ancaeus son of Lycurgus (or Poseidon by a different mother), slain in the Calydonian hunt, is a separate hero.