Valdemar was born at the end of the 1230's as the son of Jarl [ [Magnusson-193|Birger Magnusson]] and his first wife Ingeborg Eriksdottir. Ingeborg was sister with the Swedish king Erik Eriksson "Läspe och Halte" and Birger was his right-hand-man.
When Erik died, young Valdemar was elected king during the winter of 1250 and he was crowned in Linköping the following year. It was, however, his father who truly ruled until he died in 1266. Magnus, Valdemar's younger brother, became the new Jarl and helped his brother rule the country. Together they allowed the Franciscans to build a convent with the Riddarholmskyrkan in the city of Stockholm, the city that their father had founded a couple of decades earlier. 
Sofia died in 1286 and Valdemar married a woman named Lucrardis.
In 1275 war broke out between Valdemar and his brother Magnus. Valdemar was defeated at the Battle of Hova and Magnus was elected king. The dethroned brother fled to Norway and returned with support of the Norwegian and Danish kings alongside the duke of Holstein. The kingdom was devided in 1278 and Valdemar was given the southern and western parts of the country. Magnus soon took the land back and Valdemar fled to Denmark but in 1285 the church made him legally incompetent. From 1288 and onwards Valdemar was forced to live imprisoned at Nyköpingshus. The scandals caused by his continous adultery with several women was also an excuse for his imprisonment. 
Valdemar died in 1302, still imprisoned at Nyköpingshus. He is believed to have been buried in the same grave as his brother Magnus in the Franciscan convent church on Riddarholmen or at convent church in Vreta Kloster.
Valdemar was the first of his family to be elected king of Sweden. His father's home was in Bjälbo on the east coast of the lake Vettern.
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