Valdemar the Young (Danish: Valdemar den Unge) was King of Denmark from 1218 until his death.
Valdemar was the eldest son and co-ruler of Valdemar II of Denmark by his first wife, Dagmar of Bohemia. He did not outlive his father so was never a sole monarch. He is sometimes referred to as Valdemar III for example his tombstone reads in Latin: Waldemarus Tertius Rex Daniae, Filius Waldemari Secundi "Valdemar the Third, King of Denmark, son of Valdemar the Second". However, Valdemar III is more commonly used to denote a later king, Valdemar of Schleswig.