Otto I of Guelders was a nobleman from the House of Wassenberg, born around 1300. He became the Duke of Guelders in 1343 and ruled until his death in 1371. Otto was known for his efforts to strengthen the duchy and expand its territories through strategic marriages and alliances. During his reign, Otto I faced challenges from neighboring regions and worked to maintain peace and stability in Guelders. His leadership contributed to the development of the region, and he is remembered for his role in the political landscape of medieval Europe.