Valdemar Magnusson (c. after 1282 1318) was a Swedish prince, heir to the throne of Sweden, and Duke of Finland.

The Nyköping Banquet (Swedish: Nyköpings gästabud) was King Birger of Sweden's Christmas celebration 11 December 1317 at Nyköping Castle in Sweden. Among the guests were his two brothers Duke Valdemar and Duke Eric, who later that night were imprisoned and subsequently starved to death in the dungeon of Nyköping Castle.