Otto I, Count of Oldenburg (born ca.
His father was Maurice, Count of Oldenburg who died in 1209, whereupon Otto succeeded to the title along with his brother Christian II, Count of Oldenburg.
In so doing he won Moorriem, Holle, and Elsfleth from Stedingen and freed himself from the archiepiscopal sovereignty.
He also waged war on County of Hoya and on the Bishopric of Münster, the latter on a dispute over fief.
With the death of his son Heinrich in 1255, this line became extinct.