Eystein Halfdansson (Old Norse: Eysteinn Hálfdansson) was the son of Halfdan Hvitbeinn of the House of Yngling according to Heimskringla. He lived around 730, and 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 went to Varna with some ships to pillage and carried away all livestock and other valuables. However, the king of Varna was king Skjöld who was a great warlock. Skjöld 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 inherited by his son Halfdan the Mild.