Sö 86 is the Rundata catalog number for a Viking Age memorial runic inscription located in Åby, which is about one kilometer north of Ålberga, Södermanland County, Sweden, and in the historic province of Södermanland. The inscription features a depiction of the hammer of the Norse pagan god Thor named Mjöllnir and a facial mask.

Thor is a prominent god in Germanic paganism. In Norse mythology, he is a hammer-wielding god associated with lightning, thunder, storms, sacred groves and trees, strength, the protection of humankind, hallowing, and fertility. Besides Old Norse Þórr, the deity occurs in Old English as Þunor ("Thunor"), in Old Frisian as Thuner, in Old Saxon as Thunar, and in Old High German as Donar, all ultimately stemming from the Proto-Germanic theonym *Þun(a)raz, meaning 'Thunder'.