Hinn almáttki áss (the almighty áss "god") is an unknown Norse divinity evoked in an Icelandic legal oath sworn on a temple ring. This oath is especially mentioned in Landnámabók (Hauksbók 268):
Hjálpi mér svá Freyr ok Njörðr ok inn almáttki Áss
May Freyr and Njörd and the almighty ás help me
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 Ull’s ring. Rudolf Simek theorizes that this hypothesis was in contradiction with the insignificance of the cult of Ullr.
The expression could also refer to Odin, as the most important god of the Norse pantheon. But apart from the fact that his cult was not very widespread in Iceland, his unpredictable nature strongly goes against this solution.
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 and possibly regnator omnium deus).
Finally, as the oath was transmitted by a Christian author, the 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".Régis Boyer shares this opinion, underscoring that the word "almáttki" is nowhere else to be found in a pagan context.