The oldest Slavic settlements in present-day Brzeg Dolny date back to the early Middle Ages. In the 10th century the area became part of the emerging Polish state under its first ruler Mieszko I of Poland. Brzeg Dolny was first mentioned under the Old Polish name "Brzege" in a 1353 deed as a part of the Duchy of Wrocław, then within the Bohemian (Czech) Crown Lands. The Warzyń district is older, mentioned as a village in a 1261 document of Duke Henry III the White when the region was still part of medieval Piast-ruled Poland. There was a ferry crossing the Oder River in Brzeg Dolny.