In Norse mythology, Dellingr (Old Norse possibly "the dayspring" or "shining one") is a god. Dellingr is attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and in the Prose Edda, written in the 13th century by Snorri Sturluson. In both sources, Dellingr is described as the father of Dagr, the personified day. The Prose Edda adds that, depending on manuscript variation, he is either the third husband of Nótt, the personified night, or the husband of Jörð, the personified earth. Dellingr is also attested in the legendary saga Hervarar saga ok Heiðreks. Scholars have proposed that Dellingr is the personified dawn, and his name may appear both in an English surname and place name.
Jacob Grimm states that Dellingr is the assimilated form of Deglingr, which includes the name of Dellingr's son Dagr. Grimm adds that if the -ling likely refers to descent, and that due to this Dellingr may have been the "progenitor Dagr before him" or that the succession order has been reversed, which Grimm states often occurs in old genealogies. Benjamin Thorpe says that Dellingr may be dawn personified, similarly to his son Dagr, the personified day.
Regarding the references to "Delling's door" as used in Hervarar saga ok Heiðreks, Christopher Tolkien says that:
What this phrase meant to the maker of these riddles is impossible to say. In Hávamál 160 it is said that the dwarf Thjódrørir sang before Delling's doors, which (in view of the fact that Delling is the father of Dag (Day) in Vafþrúðnismál 25) may mean that he gave warning to his people that the sun was coming up, and they must return to their dark houses; the phrase would then virtually mean 'at sunrise.' As regarding dǫglings for Dellings in H, and Dǫglingar were the descendants of Dagr (according to SnE. 183).
John Lindow says that some confusion exists about the reference to Dellingr in Hávamál. Lindow says that "Dellingr's doors" may either be a metaphor for sunrise or the reference may refer to the dwarf of the same name.