Berserkers were legendary Viking warriors described in Norse literature as fighting in a trance-like fury.
The word berserker is related to Old Norse berserkr. Medieval sources portray berserkers as unusually fierce fighters, sometimes saying they entered a state of overwhelming rage or became insensitive to pain. Some accounts associate them with the god Odin.
The historical reality behind these descriptions is uncertain. Berserkers may have been a recognized warrior group, an elite or ritual identity, or a literary image used to dramatize exceptional courage and violence. The surviving evidence does not establish one single explanation.
Modern claims that berserkers routinely achieved their state by eating fly agaric mushrooms remain speculative. Norse texts also use related imagery for wolf-warriors, but berserkers and úlfheðnar are not necessarily identical categories. The term should therefore be treated as both a historical word and a literary label.