Auisle or Óisle (Old Norse: Ásl [ˈɑːsl] or Auðgísl [ˈɔuðˌɡiːsl]; died c. 867) was a Viking leader in Ireland and Scotland in the mid-late ninth century. He was the son of the king of Lochlann, identified in the non-contemporary Fragmentary Annals of Ireland as Gofraid, and brother of Amlaíb Conung and Ímar, the latter of whom founded the Uí Ímair dynasty, and whose descendants would go on to dominate the Irish Sea region for several centuries. Another Viking leader, Halfdan Ragnarsson, is sometimes considered a brother. The Irish Annals title Auisle, Ímar and Amlaíb "kings of the foreigners". Modern scholars use the title "kings of Dublin" after the Viking settlement which formed the base of their power.

Auisle is mentioned three times in contemporary annals. In the first entry, dated 863, he and his brothers are recorded as having raided Brega, including underground tombs at Achad Aldai, Cnodba, and Dubad. The second, dated 866, records Auisle and Amlaíb raiding Pictland, taking away many hostages. In the final entry, dated 867, the death of Auisle at the hands of unnamed kinsmen is reported. According to the later Fragmentary Annals his brothers Amlaíb and Ímar plotted his death, with Amlaíb striking the killing blow.

The earliest recorded Viking raids in Ireland occurred in 795. Over time, these raids increased in intensity, and they overwintered in Ireland for the first time in 840–841. Later in 841 a longphort was constructed at Áth Cliath (Irish for hurdled ford), a site which would later develop into the city of Dublin. Longphorts were also established at other sites around Ireland, some of which developed into larger Viking settlements over time. The Viking population in Ireland was boosted in 851 with the arrival of a large group known as "dark foreigners" – a contentious term usually considered to mean the newly arrived Vikings, as opposed to the "fair foreigners", i.e. the Viking population which was resident prior to this influx. A kingdom in Viking Scotland was established by the mid ninth-century, and it exerted control over some of the Vikings in Ireland. By 853 a separate kingdom of Dublin had been set up which claimed control over all the Vikings in Ireland.

Auisle's brother Amlaíb arrived in Ireland in 853 according to the Annals of Ulster:

Amlaíb, son of the king of Lochlann, came to Ireland, and the foreigners of Ireland submitted to him, and he took tribute from the Irish.

Amlaíb is named in the annals as a "king of the foreigners", but in modern texts he is usually labelled the first king of Dublin, after the Viking settlement which was the base of his power. His brothers arrived in Ireland later, and they ruled together as co-kings. The Fragmentary Annals go into more detail regarding Amlaíb's arrival:

Also in this year, i.e. the sixth year of the reign of Máel Sechlainn, Amlaíb Conung, son of the king of Lochlann, came to Ireland, and he brought with him a proclamation of many tributes and taxes from his father, and he departed suddenly. Then his younger brother Ímar came after him to levy the same tribute.

Lochlann, originally Laithlinn or Lothlend, the land where Amlaíb's father was king, is often identified with Norway, but it is not universally accepted that it had such a meaning in early times. Several historians have proposed instead that in early times, and certainly as late as the Battle of Clontarf in 1014, Laithlinn refers to the Norse and Norse-Gael lands in the Hebrides, the Isle of Man, the Northern Isles and parts of mainland Scotland. Whatever the original sense, by the twelfth century, when Magnus Barefoot undertook his expedition to the West, it had come to mean Norway.