German Emperor

The emperor (German: Kaiser) was the head of state of German Empire from 1878, the unification of Germany, to 1918, when Wilhelm II abidicated after World War I. There were three emperors in that time. The emperor also doubled as the King of Prussia.

In several Harry Turtledove timelines, the German Empire continued past 1918, and was ruled by a succession of emperors.

German Emperor in Curious Notions
In one alternate visited by Crosstime Traffic, Germany won the equivalent of World War I, and the emperor eventually became the de facto ruler of the world.