Halfdan Long-Leg (Old Norse: Hálfdan háleggur, Norwegian: Halvdan Hålegg) was a Viking-Age warrior who lived in the latter half of the 9th century.
Snorri Sturluson in Heimskringla states that Halfdan was one of Harald's many sons who were involved in a power struggle with one another.
Halfdan and his brother Gudröd the Radiant were responsible for murdering Rognvald Eysteinsson and 60 of his men by burning them inside a structure in an attempt to claim his lands.
Rognvald's son Torf-Einarr performed the Blood eagle ritual on Halfdan in retaliation after a battle.
Harald made Rognvald's son Thorir Earl of Møre and gave his daughter Alof to him in marriage.