Otto I was Duke of Austria and Styria for more than two decades in the 14th Century, sharing power with his brother Albert.

Otto was born on July 23, 1301, in Vienna. His father was Germany's Albert I, and his mother was Elizabeth of Carinthia. On May 15, 1325, Otto married Elizabeth of Bavaria. They had two children, neither of whom lived into adulthood. In 1327, to mark the birth os their first son, Frederick, Otto founded Neuberg Abbey in Styria. Elizabeth died in 1330 and was buried at the abbey church. Otto had four older brothers, three of whom ruled Austria and Styria before he did. When his older brother, Frederick II, died, in 1330, Otto took over the ruling duties of the duchies of Austria and Styria, with his older brother Albert. Those two brothers shared the rule of those two duchies.