Heorogar was a Danish king who appears in the Old English poem Beowulf

Beowulf

Beowulf , but modern scholars agree in naming it after the hero whose life is its subject." of an Old English heroic epic poem consisting of 3182 alliterative long lines, set in Scandinavia, commonly cited as one of the most important works of Anglo-Saxon literature.It survives in a single...

as the eldest son of Healfdene (halfdan), and the brother of Hroðgar

Hroðgar

Hroðgar, King Hroþgar, "Hrothgar", Hróarr, Hroar, Roar, Roas or Ro was a legendary Danish king, living in the early 6th century....

 (Hroar), and Halga

Halga

Halga, Helgi, Helghe or Helgo was a legendary Danish king living in the early 6th century. His name would in his own language have been *Hailaga ....

 (Helgi). The people in parentheses are personages found also in Norse sources.

He is mentioned in lines 2155-2165 of the poem, when King Hrothgar gives Beowulf the armour and weapons that originally belonged to King Heorogar:

"Me ðis hildesceorp Hroðgar sealde,

snotra fengel, sume worde het

þæt ic his ærest ðe est gesægde;

cwæð þæt hyt hæfde *Hiorogar cyning,

leod Scyldunga lange hwile;

no ðy ær suna sinum syllan wolde,

hwatum Heorowearde, þeah he him hold wære,

breostgewædu. Bruc ealles well!"

Translation:

"Hrothgar did not leave Beowulf unsatisfied. Beowulf offered all of the treasures given to him to Hygelac his leader. Hygelac ordered in his boar standard, a suit of armour, and a sword given to him by Hrothgar who had received it from his brother *Heorogar and once promised to Heoroweard and gave it all to Beowulf to use well."

Unlike Halga, Hroðgar, Healfdene, and Heorogar's son Heoroweard

Heoroweard

Heoroweard is a character who appears in Beowulf and also in Norse legends, where he is named Hjörvarðr or Hiartuar. If he existed in real life, his name would have been Proto-Norse *Heruwarduz....

, Heorogar does not appear in Norse sources. However, Heorogar may explain why Heoroweard (according to Norse sources) rebelled against Hroðulf (Hrólf Kraki) and killed him. As the son of Heorogar, the eldest of Healfdene's sons, Heoroweard had greater right to the Danish throne than Hroðulf.