Otto I of Nassau

Otto I (1224–1290), Count of Nassau, was a son of Henry II the Rich. With his brother Walram II he succeeded their father before 1251, and in 1255 they signed the Prima Divisio, partitioning Nassau along the Lahn; Otto took the north around Siegen.

His feuds with Rhenish lords and a quarrel over Teutonic Order estates brought him excommunication in 1285, settled the following year. By Agnes of Leiningen he left sons Henry, Emicho and John.