The Prussian mythology was a polytheistic religion of the Old Prussians, indigenous peoples of Prussia before the Prussian Crusade waged by the Teutonic Knights. It was closely related to other Baltic faiths, the Lithuanian and Latvian mythologies. Its myths and legends did not survive as Prussians became Germanized and extinct in the early 18th century. Fragmentary information on gods and rituals can be found in various medieval chronicles, but most of them are unreliable. No sources document pagan religion before the forced Christianization in the 13th century. Most of what is known about Prussian religion is obtained from dubious 16th-century sources (Sudovian Book and Simon Grunau).
The Teutonic Knights, a crusading military order, began the Prussian Crusade in the 1220s. Their goal was to conquer and convert pagan Prussians to Christianity. The Knights built log and stone fortresses, which proved to be impregnable to the Prussians. Despite five Prussian uprisings, conquest of Prussia was then complete by the 1280s. German colonists repopulated the decimated region. It is estimated that by around 1400, Prussians numbered 100,000 and comprised about half of the total population in Prussia. The Prussians were subject to Germanization and assimilation and eventually became extinct sometime after the 16th century. The Knights regarded paganism as evil, worthy of complete eradication and not study. Therefore they showed no interest in local customs and produced no detailed accounts of Prussian mythology. Bits and pieces of accidental, fragmentary, but reliable, mentions of gods and traditions can be found in official Teutonic documents and chronicles, such as the 1248 Treaty of Christburg, Chronicle of Peter von Dusburg, correspondence with the Pope.