Tapio (spirit) in the context of Tellervo

Baltic Finnic paganism, or Baltic Finnic polytheism was the indigenous religion of the various Baltic Finnic peoples, specifically the Finns, Estonians, Võros, Setos, Karelians, Veps, Izhorians, Votes and Livonians, prior to Christianisation. It was a polytheistic religion, worshipping a number of different deities. The chief deity was the god of thunder and the sky, Ukko; other important deities included Jumala, Ahti, and Tapio. Jumala was a sky god; today, the word "Jumala" refers to a monotheistic God. Ahti was a god of the sea, waters and fish. Tapio was the god of the forest and hunting.

Baltic Finnic paganism included necrolatry (worship of the dead) and shamanism (tietäjä(t), literally "one who knows"), and the religion was not always uniform across the areas it was practiced, as customs and beliefs varied during different periods of time and regions. Baltic Finnic paganism shares some features with its neighbouring Baltic, Norse and Germanic pagan beliefs.

Ukko (Finnish: [ˈukːo]), is a thunder and weather god in Finnish mythology, whose vital role is fertilizing fields with his thunder and rain.

Unto Salo [fi] believes that Ilmari, the Finnic sky god, is the origin of Ukko, but that as Ukko Ilmari experienced very significant, although far from total, influence from the Indo-European sky god especially in the form of Thor. Eemil Nestor Setälä also stated that Ukko can't be a very old name for a god and that the thunder god cult among Finns was of Germanic origin. According to Martti Haavio, the name Ukko was sometimes used as a common noun or generalised epithet for multiple deities instead of denoting a specific god. In 1789, Christfried Ganander wrote that the forest god Tapio was sometimes honoured with the name Ukko.