Valdemar Magnusson, Duke of Finland

Valdemar Magnusson (c. 1282–1318), third son of King Magnus Ladulås, was made Duke of Finland at his brother Birger's coronation in 1302. With his brother Erik he warred against King Birger: the Håtuna capture of 1306 and the Peace of Helsingborg in 1310 left the realm divided between the king and the two dukes, and in 1315 Valdemar took the east, including Stockholm.

In 1312 he married Ingeborg of Norway in Oslo. Seized with Erik at the Nyköping Banquet on 10 December 1317, he died in Nyköping Castle in 1318.