Väinämöinen was the central hero of the Kalevala — "the Eternal Sage," born of Ilmatar after his seven-hundred-year gestation, already old at his birth, the master singer whose songs could shape reality, the great shaman whose journeys to the otherworld and to the depths of the dead were the model for human shamanic practice. He had a long beard from his birth (his mother had carried him so long); he sang in a voice of supernatural power; his songs could raise mountains, make trees grow, freeze water, summon weapons, accomplish whatever the singer desired if the words were right. The Kalevala is largely the cycle of his exploits and those of his companions — the smith Ilmarinen and the warrior Lemminkäinen.

His central narrative concerns the Sampo — a magical mill or cosmic axis or universal source-of-plenty (the exact nature of the Sampo has been debated since the Kalevala's first publication; Lönnrot was unable to give a coherent definition, and the folk-tradition was apparently not unified on the point). Väinämöinen sought the Sampo from the dark land of Pohjola, ruled by the witch Louhi (treated below); he and his companions stole it after long adventure; in the pursuit by Louhi, the Sampo was broken, its fragments scattered across the sea — but the fragments themselves brought prosperity to the lands they fell upon, and Finland's good fortune was attributed to the Sampo-fragments that fell on Finnish soil.

Väinämöinen's departure from the world ended the Kalevala. He had been the great pre-Christian sage; when a new age came (a girl gave birth to a child whose true paternity was uncertain, and who was nevertheless baptized as the new king of Karelia — an obvious Christianizing parable, and one of the few overtly Christian moments in the Kalevala), Väinämöinen recognized that his time was past. He left Finland in a copper boat, sailing into the western horizon — but promised that he would return at some future need, when the Finnish people called him back. His departure is the Kalevala's final scene; the singing-tradition ends with the implication that all was as it should be, that the new age had begun, but with the great sage's promise of eventual return as a wistful coda.