The son of Gripr, a powerful farmer, and his wife Gunnlöð. They had nine sons, of whom Hrómundr was the greatest. He became a servant of king Oláfr.
When Oláfr sailed east to Norway with his fleet, they were met by six warships, the biggest of which was commanded by ugly man called Hröngviðr, who challenged them, and Oláfr accepted the challenge. Hröngviðr ran up to the king's ship and killed many of his warriors. Seeing the carnage, Hrómundr took a club in his hand, bound to himself a long goat-beard and put a hood on his head, ran forward, and killed Hröngviðr.
The fleet continued their journey and sailed to Hebrides, where they went ashore. There Hrómundr met a man who told him of the wealth hidden in a nearby barrow, which was guarded by an undead berserker called Þráinn. Hrómundr descended into the barrow and came upon the berserker, and a fight ensued. After a long battle, interspersed with insults, Hrómundr defeated Þráinn. He obtained the old man's sword Mistiltein and took from the treasure a ring and a necklace.
Hrómundr became very famous, and popular and generous. He fell in love with Svánhit, the daughter of king Oláfr. Certain men slandered him to the king and when this became too much, he and his brothers abandoned the king's retinue and returned home to their father. Svánhit later convinced him and his brothers to come to the assistance of Oláfr in his fight with king Haldingr. He there met Helgi the Valiant, the brother of Hröngviðr. Helgi's mistress Lára always helped him with her magic, but when Helgi accidentally cut off her leg with his sword she died. The stroke also wounded Hrómundr, but with Mistiltein he cleaved Helgi's helmet and skull. Hrómundr then fought so fiercely and felled so many men, that the army of Haldingr fled. He also killed the wizard Váli but lost his sword Mistiltein.
Hrómundr returned to his tent and was found there by Svánhit, who dressed his wound. She took him to a healer named Hagall and his wife and they healed him. Hagall often went fishing and one day caught a pike, and when he came home and cut open the fish he found in its mouth Mistiltein. Thus Hrómundr was reunited with his sword.
The last act in the saga is that Hrómundr joined Oláfr in an expedition against king Haldringr. The latter was skilled in magic and each time Hrómundr struck him, the flat of the sword struck him instead. Then Hrómundr took a club and killed him. They took Haldingr's gold and other wealth and sailed home. Oláfr gave Svánhit in marriage to Hrómundr, and they had many children. From them, royal dynasties and great warriors trace their lineage.
- Hrómundar saga Gripssonar, 3-4.