Harald III Hen (c. 1040 – April 17, 1080) is King of Denmark from 1074 to 1080.

Harald III is an illegitimate son of Danish king Sweyn II Estridsson, and contests the crown with some of his brothers.

He is a peaceful ruler who initiates a number of reforms.

Harald is married to his cousin Margareta Hasbjörnsdatter, but does not leave any heirs, and is succeeded by his brother Canute IV the Saint.

Four of his half-brothers are in turn crowned Danish kings.