The Finnish underworld was called Tuonela — "the Place of Tuoni" — and its king and queen were Tuoni and Tuonetar, the Lord and the Lady of Death. Tuonela lay across a great dark river, the river Tuoni, that no living person might cross; it was the destination of all souls when they died, and there they remained, ruled by the dread pair, in shadowy halls deep in the earth or far in the cold north.

The figures of Tuoni and Tuonetar were less elaborated than the Greek Hades and Persephone — the Finnish imagination had no marriage-myth, no abduction story, no mythology of the underworld's foundation. They simply were: the rulers of the place where the dead went. Tuonetar in particular played a role in the great epic of the Kalevala, when the hero Väinämöinen journeyed to Tuonela to recover the words of an old spell and was nearly held there by Tuonetar, who served him a bowl of beer in which she had hidden serpents and frogs; only by a counter-charm did he escape.

The river of Tuonela had a black swan upon its waters — the Swan of Tuonela — that swam in slow circles, singing as it went; whoever heard the swan's song understood that he was already across the river, already in the realm of the dead. The hero Lemminkäinen, in another Kalevala episode, attempted to shoot the swan with an arrow, that he might prove his manhood; he was killed for the attempt, his body torn into pieces, and only by the long search of his mother who walked through Tuonela gathering up the pieces and singing them back together was he restored to life.

Tuoni and Tuonetar had children: Tuonen tytti, the daughter of Tuoni, who was sometimes the ferrywoman of the dark river; Loviatar, who in some traditions was Tuonetar's daughter and the mother of the nine diseases; and various other shadowy figures of the underworld. The ensemble forms a less elaborated but recognizable Finnish counterpart to the underworld pantheons of other Indo-European peoples, retained in folk-belief into the modern period.