Laguz is the twenty-first rune of the Elder Futhark, fifth in the third aett, carrying the phoneme "l." Its reconstructed name means water, a lake or the sea. The rune poems describe water as seeming endless to those the ship tosses, the sea that terrifies and will not be tamed, an image of a vast, flowing element. The rune gathers ideas of water, flow, the tides and, in later tradition, the depths of the unconscious.
Laguz stands fifth in the aett of Tyr. Its Old English futhorc counterpart, lagu, meaning water or sea, receives a stanza in the Old English Rune Poem describing the sea as endless to men who must venture upon an unsteady ship, so that the waves greatly terrify them and the sea-horse, the ship, heeds not its bridle. Laguz survived into the Younger Futhark as logr, and appears in both the Norwegian and Icelandic Rune Poems, the latter associating it with a whirling stream and a great geyser.
Runologists reconstruct the Proto-Germanic form behind the name as *laguz, part of the comparative linguistic evidence, alongside cognate vocabulary across the older Germanic languages, used to establish the name's original sense independent of the later rune poems themselves.