Hrólfr Kraki (Old Norse: [ˈhroːlvz̠ ˈkrɑke]), Hroðulf, Rolfo, Roluo, Rolf Krage (early 6th century) was a semi-legendary Danish king who appears in both Anglo-Saxon and Scandinavian tradition.

Both traditions describe him as a Danish Scylding, the nephew of Hroðgar and the grandson of Healfdene. The consensus view is that Anglo-Saxon and Scandinavian traditions describe the same people. Whereas the Anglo-Saxon Beowulf and Widsith do not go further than treating his relationship with Hroðgar and their animosity with Froda and Ingeld, the Scandinavian sources expand on his life as the king at Lejre and on his relationship with Halga, Hroðgar's brother. In Beowulf and Widsith, it is never explained how Hroðgar and Hroðulf are uncle and nephew.

The poem Beowulf introduces Hroðulf as kinsman. Later, the text explains that Hroðulf is Hroðgar's nephew and that "each was true to the other". Hroðgar is given three siblings, brothers Heorogar and Halga and an unnamed sister, all the children of Healfdene and belonging to the royal clan known as the Scyldings. The poem does not indicate which of Hroðgar's siblings is Hroðulf's parent, but later Scandinavian tradition establishes this as Halga.

Hroðgar and queen Wealhþeow had two young sons, Hreðric and Hroðmund, and Hroðulf would be their guardian in case Hroðgar dies. In a deliberately ironic passage it appears that the queen trusts Hroðulf, not suspecting that he will murder her sons to claim the throne for himself:

No existence of any Hreðric or Hroðmund, sons of Hroðgar, has survived in Scandinavian sources (although Hreðric has been suggested to be the same person as Hroerekr/Roricus, a Danish king generally described as a son or successor of Ingjald). This Hroerekr is sometimes said to have been killed by Hrólfr, vindicating the foreshadowing in Beowulf.

The Scyldings were in conflict with another clan or tribe named the Heaðobards led by their king Froda and his son Ingeld. It is in relation to this war that Hroðulf is mentioned in the other Anglo-Saxon poem where he appears, Widsith.

A common identification is that Hrólf Kraki is the same as the character Hroðulf (Hroðgar's nephew) in Beowulf. There seems to be some foreshadowing in Beowulf that Hroðulf will attempt to usurp the throne from Hroðgar's sons Hreðric and Hroðmund, a deed that also seems to be referred to in Saxo Grammaticus's Gesta Danorum (Book 2), where we find: "... our king, who laid low Rorik, the son of Bok the covetous, and wrapped the coward in death." Rorik is the form we would expect Hreðric to take in Danish and we find personages named Rorik or Hrok or similar in most version of the Hrólf Kraki tradition, but differently accounted for, seemingly indicating that Scandinavian tradition had forgotten who exactly Hreðric/Rorik/Hrok was and various story tellers subsequently invented details to explain references to this personage in older poems. The future slaying of Hreðric may be the occasion of the future burning of the hall of Heorot in the beginning of the poem – though some take it instead to refer to the legendary death of Hrólf Kraki, who in Icelandic sources is said to have died in the burning of his hall by his brother-in-law Hjörvard.

The standard view is that, if Beowulf himself has a 'cognate' character in Rolf Kraki's story, it is Bödvar Bjarki (Bodvar Biarke), who also has a younger companion, Hjalti (Hialte) – perhaps matching the Beowulf character Wiglaf. Beowulf comes from Geatland (= Götaland) and one of Bödvar Bjarki's elder brothers, Thorir, becomes a king of Götaland. Moreover, like Beowulf, Bödvar Bjarki arrives in Denmark from Götaland (Geatland), and upon arriving in Denmark he kills a beast that has been ravaging the Danish court for two years. The monster in Hrólf Kraki's saga, however, is quite unlike the Grendel of Beowulf; but it does have characteristics of a more typical dragon, a creature which appears later in Beowulf. Just as Beowulf and Wiglaf slay a dragon at the end of Beowulf, Bödvar Bjarki and Hjalti help each other slay the creature in Denmark.