Magnus Ladulås

Magnus Ladulås (pronounced ['lɑːdɵloːs], lit. 'Barnlock'), also known as Magnus Birgersson (c. 1240 – 18 December 1290), was King of Sweden from 1275 until his death in 1290.

A son of Birger Jarl and Ingeborg Eriksdotter, Magnus became king after he and his brother Erik Birgersson rebelled against their elder brother, King Valdemar, in 1275. Valdemar was defeated at the Battle of Hova, and Magnus was acclaimed king later that year. Following Magnus's death in 1290, he was succeeded by his ten-year-old son Birger, during whose minority Sweden was governed by a regency headed by Torgils Knutsson.

Medieval Swedish kings did not use regnal numbers as part of their title. In modern literature he may be referred to as either Magnus I or Magnus III.

Source: Wikipedia — https://en.wikipedia.org/wiki/Magnus_Ladul%C3%A5s