Magnus III of Sweden

Magnus III
Bust of Magnus as duke at Skara Cathedral
King of Sweden
Reign	1275 - 18 December 1290
Predecessor	Valdemar Birgersson
Successor	Birger Magnusson
Born	1240
Died	18 December 1290 (aged 49–50)
Burial	Riddarholm Church
Spouse	N.N. Helwig of Holstein
Issue	with unknown wife: Eric Magnusson with Helwig of Holstein: Ingeborg, Queen of Denmark Birger, King of Sweden Eric, Duke of Sudermannia Valdemar, Duke of Finland Richeza Magnusdotter of Sweden, Abbess of St. Clare's Priory
House	House of Bjelbo
Father	Birger Jarl
Mother	Ingeborg Eriksdotter of Sweden
Religion	Roman Catholicism

Magnus III (Swedish: Magnus Birgersson/Magnus Ladulås; 1240 – 18 December 1290) was King of Sweden from 1275 until his death in 1290.

He was the "first Magnus" to rule Sweden for any length of time, not generally regarded as a usurper or a pretender (but third Magnus to have been proclaimed Sweden's king and ruled there). Later historians ascribe his epithet "Ladulås" – Barnlock – to a decree of 1279 or 1280 freeing the yeomanry from the duty to provide sustenance for travelling nobles and bishops ("Peasants! Lock your barns!"); another theory is that it's a corruption of Ladislaus, which could possibly have been his second name, considering his Slavic heritage.

Referring to Magnus Ladulås as Magnus I is an invention not recognized by any Swedish historians today. The Swedish kings Eric XIV (1560–68) and Charles IX (1604–1611) took their numbers after studying a partially fictitious History of Sweden designed as propaganda during their father's reign, but that has no bearing on the enumeration of Magnus III.

Magnus, whose birth year has never been confirmed in modern times, was probably the second son of Birger Jarl (Birger Magnuson, 1200–66) and Ingeborg, herself the sister of the childless King Eric XI and daughter of King Eric X. His father designated Magnus as his successor in powers of the Jarl, henceforward titled Duke of Sweden. The (probably) elder brother, Valdemar, had become king succeeding their maternal uncle in 1250.

In 1275, Duke Magnus started a rebellion against his brother with Danish help, and ousted him from the throne. Magnus was elected king at the Stones of Mora. In 1276, Magnus Barnlock allegedly married a second wife Helwig, daughter of Gerard I of Holstein. Through her mother, Elizabeth of Mecklenburg, Helwig was a descendant of Christina, the putative daughter of King Sverker II). A papal annulment of Magnus' alleged first marriage and a dispensation for the second (necessary because of consanguinuity) were issued ten years later, in 1286. Haelwig later acted as regent, probably 1290–1302 and 1320–1327.