Slavic mythology is the mythological aspect of the polytheistic religion that was practiced by the Slavs before Christianisation.
Unlike ancient Greek, Hindu, Chinese or Egyptian mythology, there are no first-hand records for the study of Slavic mythology. It has not been proven that the Slavs had any sort of writing system before the arrival of Saints Cyril and Methodius to Slavic lands in 862. Therefore, all their original religious beliefs and traditions were likely passed down orally over the generations, and basically forgotten over the centuries following their rapid conversion into Christianity (which began with the conversion of Bulgaria in 864 and was largely complete by the late 11th century.) Before that, sparse records of Slavic religion were mostly written by non-Slavic Christian missionaries. Archaeological remains of old Slavic cult images and shrines have been found, though little can be yielded from them without legitimate knowledge of their contexts, other than confirming existing historical records. Fragments of old mythological beliefs and pagan festivals survive up to this day in folk customs, songs, stories and folk-tales of all the Slavic nations.
There are currently no known written accounts of Slavic mythology predating the fragmentation of the Proto-Slavic people into West, East, and South Slavs, with the possible exception of a short note in Herodotus’s Histories, mentioning the tribes of Budini and Neuri in the far north, whose men supposedly transform themselves into wolves for several days each year. Although Herodotus is himself not convinced by this rumour, he stresses that he has heard some swear it. Some researchers have interpreted this through the Slavic folk belief in werewolves, while others believe that Herodotus actually referred to ancient Slavic carnival festivals, when groups of young men roamed the villages in masks, sometimes referred to as vucari (wolf-humans). The identification of "Neuri" with Proto-Slavs remains controversial, however.