The son of Iðmundr, a jarl in service of king Hjörvarðr. Hjörvarðr was told that king Sváfnir of Svávaland had a daughter of incomparable beauty, named Sigrlinn. Atli was sent to Sváfnir's court to demand Sigrlinn's hand for the king. One of Sváfnir's jarls, Fránmarr, who was the foster-father of Sigrlinn, advised that the maiden should be refused and Atli returned home.
One day, as he was standing in a grove, a bird spoke to him. The bird offered to help him in exchange for whatever he chooses from the king's court. Atli then went back to Sváfnir's country, and this time Hjörvarðr went with him. When they came to Svávaland, they found it under attack by King Hróðmarr, who desired Sigrlinn for himself. They set up camp near the river. Atli crossed the river and came upon a house, guarded by an eagle, but it was asleep. He shot the large bird — which was Sváfnir's jarl Fránmarr in eagle form — and went inside the house. He there found Sigrlinn and another maiden, Álof, the daughter of Fránmarr. He brought both women with him; Hjörvarðr took Sigrlinn and Atli took Álof.
Atli later joined Hjörvarðr's son Helgi in avenging the death of Sigrlinn's father. After Helgi killed the jötunn Hati, the heroes engaged in a heated contest of flyting with the jötunn's daughter Hrímgerðr.
- Helgakviða Hjörvarðssonar.