Algiz is a reconstructed Proto-Germanic name for the ᛉ rune, representing Proto-Germanic final z. The rune is a special case because, like the Ing-rune, it could not be named acrophonically, since the sound it represents does not occur word-initially. Proto-Germanic z (continuing Proto-Indo-European final s) also soon became obsolete, and the rune is usually transcribed as Proto-Norse R. The sound became regular word-final r in Old Norse, and the existence of the algiz rune is the only indication that there was still a phonemic difference between the two in Proto-Norse times (roughly in the 8th century).

The name Algiz means "elk", but the reconstruction is rather uncertain. In the rune poems of the Young Futhark, the rune is already lost, but in the Gothic alphabet the letter z is called ezec, which could be cognate to "elk".

The rune survives in its original shape in the Anglo-Saxon runic alphabet, as ᛉ Eolh, representing a χ-sound. In the Anglo-Saxon rune poem, it is glossed as

Eolh-secg eard hæfþ oftust on fenne / wexeð on wature, wundaþ grimme / blode breneð beorna gehwylcne / ðe him ænigne onfeng gedeþ.
"The Eolh-sedge is mostly to be found in a marsh; it grows in the water and makes a ghastly wound, covering with blood every warrior who touches it."

Eolh-secg "elk-sedge" was probably pronounced with a [χ] in sandhi. The reconstructed Proto-Germanic name algiz "elk", based on the names of the Anglo-Saxon (of the same shape, but with a different sound) rune and the Gothic letter (with a different shape but the same sound) is rather tenous, since almost any masculine noun could have been picked in Proto-Germanic to represent the word-final z-sound.

In the Young Futhark there is Yr ᛦ "yew", probably related to ᛉ, but with its sound changed from word-final r to y (see also Eihwaz). The shape of the algiz rune is taken up by Young Futhark Maðr (accusative: man) ᛘ ("man"), replacing Old Futhark ᛗ Mannaz. In Neo-Pagan systems of divination based on the runes, Algiz is commonly seen as an auspicious rune symbolizing life or protection, and consequently the upturned Yr rune is sometimes called a "death rune", somewhat ironically, since Maðr and Yr are probably unrelated, and there is no evidence that reversed symbols were used to represent inverse concepts in early systems of symbolism (see also sauwastika).

The Algiz rune plays a certain role in Fascist symbolism.