German monarchs were rulers of various German states and territories before the establishment of the German Empire in 1871. The most notable monarchs included the Holy Roman Emperors, who ruled over a vast territory in Central Europe, and the kings of Prussia, which played a significant role in unifying Germany. The German monarchy ended with the abdication of Kaiser Wilhelm II in 1918, following Germany's defeat in World War I. This led to the establishment of the Weimar Republic, marking the transition from monarchy to a democratic government in Germany.