In Norse mythology, Gjallarhorn (Old Norse: [ˈɡjɑlːɑrˌhorn]; "hollering horn"[1] or "the loud sounding horn"[2]) is a horn associated with the god Heimdallr and the wise being Mímir. The sound of Heimdallr's horn will herald the beginning of Ragnarök, the sound of which will be heard in all corners of the world. Gjallarhorn is attested in the Poetic Edda, compiled in the 13th century from earlier traditional material, and the Prose Edda, written in the 13th century by Snorri Sturluson.