Magnus I (1304–1369), called the Pious (Latin Pius), was a notable German noble from the House of Welf, a powerful dynasty in medieval Germany. He was the ruler of the Principality of Brunswick-Wolfenbüttel, a part of the larger Duchy of Brunswick-Lüneburg. Magnus was a key figure in the Welf dynasty’s efforts to consolidate their territorial holdings during a time of political fragmentation in the Holy Roman Empire.