berserker, in premedieval and medieval Norse and Germanic history and folklore, a member of unruly warrior gangs that worshipped Odin, the supreme Norse deity, and attached themselves to royal and noble courts as bodyguards and shock troops.
The berserkers’ savagery in battle and their animal-skin attire contributed to the development of the werewolf legend in Europe. It is unclear whether the berserker warriors wore bear and wolf skins into battle or fought bare-chested (i.e., without byrnies or mail shirts); tapestries and other sources represent both possibilities. The berserkers were in the habit of raping and murdering at will in their host communities (thus going “berserk”), and in the Norse sagas they were often portrayed as villains. In an Old Norse poem, most of which dates from the 9th century, berserkers are recorded as the household guard of Norway’s king Harald I Fairhair (reigned 872–930).