In 986 Zeven was first mentioned in a document of the Benedictine in Heeslingen, then giving its name as "kivinan à Heeslingen" (Kivinan near Heeslingen). In 1141 the convent was relocated to Zeven. The convent played a determining role in Zeven's history. Zeven belonged to the old Duchy of Saxony and at its dissolution in 1180 Zeven became a part of the newly founded Prince-Archbishopric of Bremen, the princely territory of imperial immediacy ruled by the respective holder of the archiepiscopal see of Bremen. During the Protestant Reformation the majority of the nun clung to Catholicism, while most laymen adopted Lutheranism.