Baltic mythology generally covers the pre-Christian mythology of the Latvians, Lithuanians and Old Prussians, which are thought to have at least some common roots.
The predominant common feature is polytheism, with a variety of mythical creatures and a strong presence of the spirits of the dead. Research has uncovered close relationships with the pre-Christian myths of other Indo-European peoples, especially with the Slavs, Germanic and Celts.
Both Latvia and Lithuania have state-recognized traditional religious communities with roots in the pre-Christian traditions. Various texts are sources of Baltic mythological folklore. These are largely collected and fixed in writing, but still little explored in comparison with the greater religious communities.
In Latvia, these texts are very numerous, especially the Daina. A Daina consists of four lines, each line containing eight syllables (occasionally five or six syllables). The most important collection of such folksongs are "Latvju dainas" of Krišjānis Barons. Because of their quantity (approximately 2 million) and variety, they give a very detailed and comprehensive picture of the nature-loving life, archaic ideas, customs and festivals of the Latvian tribes. The Lithuanian Dainos are much longer, and they also have ballad-like elements.
Other sources, both Latvian and Lithuanian, are in fairy tales, myths and legends, also place names and religious terms, revealed by etymological analysis. Tacitus wrote around 45 CE that the Baltic peoples worship "the mother of the gods" and use as statues of boars in the practice of their religion. Older possible sources do not clearly delineate whether it is indeed the Baltic tribes which are referenced.