Valdemar IV Atterdag (the epithet meaning "A New Dawn") or Waldemar; Danish: Valdemar Atterdag, was King of Denmark from 1340 to 1375.
He was the youngest son of Christopher II and spent most of his childhood and youth in exile at the court of Louis IV, Holy Roman Emperor in Bavaria after the defeats of his father and the death and imprisonment, respectively, of his two older brothers Eric and Otto at the hand of the Holsteiners. Here he acted as a pretender waiting for a comeback.
Following the assassination of Count Gerhard III by Niels Ebbesen and his brothers, Valdemar was proclaimed King of Denmark at the Viborg Assembly (landsting) on St Hans Day, 24 June 1340 led by Niels Ebbesen. By his marriage with Helvig, the daughter of Eric II, Duke of Schleswig, and with what was left to him by his father, he controlled about one quarter of the territory of Jutland north of the Kongeå river.
Valdemar died at Gurre Castle in north Zealand on 24 October 1375 and was buried at Sorø Abbey.