Duke Eric I of Schleswig was a nobleman who ruled in the late 12th century. He was part of the House of Knýtlinga, a dynasty that descended from the Viking kings of Denmark. Eric I's reign was marked by his efforts to strengthen the duchy of Schleswig, which is located in present-day northern Germany and southern Denmark. Eric I was known for his political alliances and military campaigns, which aimed to expand his territory. He played a significant role in the regional power dynamics of Scandinavia during his time, navigating relationships with neighboring rulers and influencing the history of the area.