Otto was one of the most powerful East Franconian princes by inheritance: having extensive land in the Radenzgau and Schweinfurt.
In 1014, he first appears as count of Lower Altmühl (or Kelsgau) and, in 1024, he inherits his father's march.
From then on to his appointment to Swabia, he takes part in many imperial expeditions into Bohemia, Hungary, and Poland.
[a] At Ulm in January 1048, the Emperor Henry III appointed him duke of Swabia after a brief vacancy following the death of Otto II.
He was engaged to marry Matilda, daughter of Boleslaus I of Poland, in 1035, but this was put off in favour of a marriage to Immilla, a daughter of Ulric Manfred, Margrave of Turin, as part of Henry's Italian plans.