Perun is a pagan god of the Slavs and Balts, the supreme god of Kievan Rus in the 9th-10th centuries, the lord of heaven, the ruler of thunder and lightning, the god of fertility, and later the patron saint of princes and their warriors, military affairs. Perun became the supreme god of all Kievan Rus during the reign of Princes Igor, Svyatoslav, and Vladimir the Great, supplanting local deities from different regions from this status. Perun's father was believed to be Belobog.Functionally, Perun is analogous to the thunder gods of other Indo-European peoples: Greek Zeus, Roman Jupiter, Germanic Thor, Indian Indra. There are suggestions of Perun's kinship with the ancient Greek celestial titan Hyperion. Perun's main functions are to control lightning, thunder, and the pouring of rain on the earth. He also took over Svarog's patronage of fire and iron, the military squad and its leader (prince), from where his parallels with Roman Mars and Celtic Taranis come. The acquisition of military functions by Perun, as well as the status of the supreme deity, occurred as a result of the increasing influence of the warrior class. It is likely that Perun had several regional and seasonal hypostases, which in the mythology of the Baltic Slavs split into separate gods, such as Prove. Yarilo, possibly, was the spring hypostasis of Perun.
Perun was depicted as a tall, muscular man with a long beard and hair. He was often depicted wearing a helmet and carrying a hammer or axe, which were his weapons. He was also associated with the color blue, which was often used to represent him in art.