John I, Duke of Saxony

John I Johann I. von Sachsen, Engern und Westfalen (de)
officially: Duke of Saxony, Angria and Westphalia colloquially: Duke of Saxe-Lauenburg
Coat-of-arms of John I
Duchy of Saxony (joint rule with his younger brother Albert II)
Joint Reign	1260–1282
Predecessor	Albert I, Duke of Saxony
Successors	Albert II with John I's sons Eric I, John II and Albert III (joint rule)
Born	1249
Died	30 July 1285 Wittenberg upon Elbe
Saxon consort	Ingeborg Birgersdotter of Småland
Issue Detail	Helen (*c. 1272–1337*) Elisabeth (*c. 1274–1306*) Eric I John II Albert III Sophia (*?–1319*)
House of	Ascania (by birth)
Father	Albert I, Duke of Saxony
Mother	Helen of Brunswick and Lunenburg
Religion	Roman Catholic

Duke John I of Saxony (1249 – 30 July 1285, Wittenberg upon Elbe) was the elder son of Duke Albert I of Saxony and his third wife Helen of Brunswick and Lunenburg, a daughter of Otto the Child. John and his younger brother Albert II jointly ruled the Duchy of Saxony after the death of their father Albert I in 1260.

In 1269, 1272, and 1282 the brothers gradually divided their governing competences within the three territorially unconnected Saxon areas (one called Land of Hadeln around Otterndorf, another around Lauenburg upon Elbe and the third around Wittenberg), thus preparing a partition. As part of this arrangement John I became Burgrave of Magdeburg in 1269.

In the imperial election in 1273, Albert II represented the jointly ruling brothers. John I resigned in 1282 in favour of his three minor sons Eric I, John II and Albert III. Later John I entered the Franciscan monastery in Wittenberg, becoming its warden (guardian), which position he held until he died. John I's sons and their uncle Albert II continued the joint rule in Saxony, with the sons entering into the government on growing major. The last document, mentioning Albert II with his nephews as Saxon fellow dukes dates back to 1295.

In 1270, John married Ingeborg Birgersdotter of Småland (*c. 1253–30 June 1302*, Mölln), a daughter or grandchild of Birger jarl. They had eight children, among them the following: