thumb|upright=1.3|Look at them, troll mother said. Look at my sons! You won't find more beautiful trolls on this side of the moon. (1915) by [[John Bauer (illustrator)|John Bauer]]
A troll is a being in Nordic folklore, including Norse mythology. In Old Norse sources, beings described as trolls dwell in isolated areas of rocks, mountains, or caves, live together in small family units, and are rarely helpful to human beings.
In later Scandinavian folklore, trolls became beings in their own right, where they live far from human habitation, are not Christianized, and are considered dangerous to human beings. Depending on the source, their appearance varies greatly; trolls may be ugly and slow-witted, or look and behave exactly like human beings, with no particularly grotesque characteristic about them.
In Scandinavian folklore, trolls are sometimes associated with particular landmarks (sometimes said to have been formed by a troll having been exposed to sunlight). Trolls are depicted in a variety of media in modern popular culture.
Etymology
The Old Norse nouns troll and trǫll (variously meaning "fiend, demon, werewolf, jötunn") and Middle High German troll, trolle "fiend" (according to philologist Vladimir Orel, the word is likely borrowed from Old Norse), possibly developed from Proto-Germanic neuter noun *trullan, meaning "to tread, step on". The origin of the Proto-Germanic word is unknown. Additionally, the Old Norse verb trylla 'to enchant, to turn into a troll' and the Middle High German verb trüllen "to flutter" both developed from the Proto-Germanic verb *trulljanan, a derivative of *trullan. The Prose Edda book Skáldskaparmál describes an encounter between an unnamed troll woman and the 9th-century skald Bragi Boddason. According to the section, Bragi was driving through "a certain forest" late one evening when a troll woman aggressively asked him who he was, in the process describing herself: