Duke Eric I, also known as Eric the Good, was a ruler of the Duchy of Schleswig in the late 10th century. He was a member of the House of Knýtlinga, a dynasty that included several notable Scandinavian kings. His reign is often remembered for efforts to strengthen the duchy and promote Christianity in the region. Eric I was the son of King Sweyn Forkbeard and Queen Świętosawa, which connected him to significant royal lineages in Denmark and Poland. His leadership was marked by attempts to maintain peace and stability, although his rule faced challenges from rival factions and external threats.