In the Gallo-Roman religion, Alaunus or Alaunius is a Gaulish god of healing and prophecy. His name is known from inscriptions found in Lurs, Alpes-de-Haute-Provence in southern France (in the dative form Αλα[υ]νειουι) and in Mannheim in western Germany. In the latter inscription, Alaunus is used as an epithet of Genius Mercury.
The name of this deity is also found as a toponym and hydronym. In Roman times in its feminine form, for example, it was used to refer to Roman Valognes in Normandy, Roman Maryport in Cumbria, Roman Alcester in Warwickshire, Roman Watercrook in Natland, Cumbria, Ardoch in Perthshire, and the River Aln in Northumberland (where the feminine form is taken by the Roman fort Alauna, now known as Lower Learchild, near where the Devil's Causeway crosses the River Aln on the modern A697 road).
The etymology of the name has never been ascertained and authorities differ over their interpretation. A connection with the Proto-Celtic root *alo- 'feed, raise' (Old Irish alid 'feed, raise', Middle Welsh alu 'bear young', Middle Breton halaff 'bear young, calve') has been made, but Matasović suggests that this is an uncertain link.
- Ellis, Peter Berresford, Dictionary of Celtic Mythology(Oxford Paperback Reference), Oxford University Press, (1994): ISBN 0-19-508961-8
- Wood, Juliette, The Celts: Life, Myth, and Art, Thorsons Publishers (2002): ISBN 0-00-764059-5