The Duke of Brunswick is a title associated with the historical region of Brunswick in northern Germany. The title has been held by various noble families, primarily the House of Welf, which played a significant role in the region's history. The Duke's authority often extended over the surrounding territories, influencing local governance and culture. The most notable Duke of Brunswick was Charles I, who ruled in the 19th century and was known for his military leadership and efforts to modernize the duchy. The title has since become largely ceremonial, with the last reigning duke, Ernest Augustus, abdicating in 1918 following the end of the German monarchy.