Almáttki áss (the almighty áss "god") is an unknown Norse god evoked in an Icelandic legal oath sworn on a temple ring, mentioned in Landnámabók (Hauksbók 268).
The reference in Landnámabók is found in a section describing the old heathen laws for how one should swear legal oaths:
The identity of this divinity has given rise to much speculation.
The identification with Thor is by far the most common. The adjective "almighty" applies particularly well to him and he had a prominent position by the time of the settlement of Iceland.
The almáttki áss can be identified with Ullr for in Atlakviða (30) Gudrún mentions the oaths Gunnar sworn by Ullr's ring. Rudolf Simek theorizes that this hypothesis was in contradiction with the insignificance of the cult of Ullr.[1]
The expression could also refer to Odin, represented in much of the Old Norse corpus as the most important god of the Norse pantheon.
Rudolf Simek also suggested that the almáttki áss might be Týr. Even if this god was little known in Iceland, the oath was a legal one and Týr was historically linked to law (cf. Mars Thingsus).
Finally, as the oath was transmitted by a Christian author, the Norse, Old: almáttki áss could have a Christian meaning. John Lindow thus suggested that maybe the author "meant the 'almighty áss' to be a noble pagan anticipation of the new religion that was to come".[2] Régis Boyer shares this opinion, underscoring that the word "almáttki" is nowhere else to be found in a pagan context.[3]