Magnus I may refer to:
Magnus the Good (1024–1047), King of Norway and King of Denmark Magnus Erlendsson, Earl of Orkney (ruled from 1108 to about 1115) Magnus the Strong, King of Sweden (c. 1106–1134) Magnus Ladulås, King of Sweden (1240–1290) Magnus, Duke of Saxony (c. 1045–1106) Magnus I, Duke of Saxe-Lauenburg from the Ascanian House (1470–1543) Magnus I, Duke of Mecklenburg Magnus, Duke of Östergötland, prince of Sweden (1542–1595)