Hæþcyn (d. 514 or 515) was the son of the Geatish king Hreðel in Beowulf. The hero Beowulf was his nephew. Hæþcyn killed his elder brother Herebeald with an arrow in a hunting accident, which caused their father Hrethel to die from grief. Then Hæþcyn became king of Geatland.

Hæþcyn was killed fighting with the Swedish king Ongenþeow, and his warriors sought refuge in Ravenswood. They were rescued by Hygelac who arrived the next day with reinforcements. His warrior Eofor killed the Swedish king. Hæþcyn was succeeded by Hygelac.