Aun the Old is a mythical Swedish king of the House of Yngling in the Heimskringla. Aun was the son of Jorund, and had ten sons, nine of which he was said to have sacrificed in order to prolong his own life. Based on the internal chronology of the House of Yngling, Aun would have died late in the fifth century. He was succeeded by his son Egil Vendelcrow identified with Ongentheow of the Beowulf narrative and placed in the early sixth century.

The Ynglings were a dynasty of kings, first in Sweden and later in Norway, primarily attested through the poem Ynglingatal. The dynasty also appears as Scylfings in Beowulf. When Beowulf and Ynglingatal were composed sometime in the eighth to tenth centuries, the respective scop and skald (poet) expected his audience to have a great deal of background information about these kings, which is shown in the allusiveness of the references.