[1] Otto was born in Marburg, a son of Henry I, Landgrave of Hesse and his first wife Adelheid of Brunswick-Lunenburg.

Following the death of his father in 1308, he inherited Upper Hesse, the "Land on the Lahn", which included Marburg, Giessen, Grünberg and Alsfeld.

Otto had a long conflict with the Archbishop of Mainz, Matthias von Bucheck.

In 1327, Mainz adopted Giessen with the help of troops from the Electorate of Trier, but the citizens of the town quickly enabled Otto to regain control.

Only after Otto's victory at Wetzlar and with the mediation of King John of Luxembourg in 1328 was conciliation made possible.