Harald 'Klak' Halfdansson was a king in Jutland around 812–814 and again from 819–827.

Gudfred was a ninth century Danish king who reigned from at least 804 to 810. Alternate spellings include Godfred (Danish), Göttrick (German), Gøtrik (Danish), Gudrød (Danish), and Godofredus (Latin). He stands at the threshold of the History of Denmark in the sense that he is the first ruler about whom there is substantial knowledge from contemporary sources. He waged offensive war against the Carolingian Empire with some success, but was murdered under murky circumstances before a major confrontation had taken place. There is no unambiguous trace of Gudfred in the later Norse sagas, and his history can only be traced from the hostile Frankish texts which makes an assessment of his role problematic. His paternity is unknown but he may have been closely related to Sigfred, who preceded him as king of Denmark c. 770–804. He was the uncle of the later Danish King Hemming (810–812) and the father of King Horik I (813–854).