Eystein Halfdansson (Old Norse: Eysteinn Hálfdansson) was the son of Halfdan Hvitbeinn of the House of Yngling according to Heimskringla. He inherited the throne of Romerike and Vestfold.
His wife was Hild, the daughter of the king of Vestfold, Erik Agnarsson. Erik had no son, so Eystein inherited Vestfold.
Eystein died while pillaging in Varna. King Skjöld of Varna, a great warlock, arrived at the beach and saw the sails of Eystein's ships. He waved his cloak and blew into it which caused a boom of one ship to swing and hit Eystein so that he fell overboard and drowned. His body was salvaged and buried in a mound. Eystein was succeeded by his son Halfdan the Mild.