The vilkacis is a werewolf in Latvian and Lithuanian mythology.
Vilkacis litterally means "wolf's eyes" 'werewolf'. Alternative names include Vilkatas, Vilkatis.
The vilkacis is a human that shapeshifts into a werewolf, however it is not clear wether there is a physical transformation or the soul enter the body of a wolf. Some tales mention an apparently asleep person who appeared at miles "running like werewolf", after what the person turns out to be dead, as the soul couldn't enter the flesh to return.
Although mostly malevolent, on occasion the vilkacis would bring treasures or be beneficial.