Hohenzollern, a dynasty of kings of Prussia, 1701–1918, and kaisers (emperors) of Germany, 1871–1918. The Hohenzollerns originated as minor nobles in southwestern Germany during the 11th century. They were named for their ancestral castle. In 1415 a younger member of the house became elector of Brandenburg. Another Hohenzollern gained Prussia in 1525. Both territories were united by inheritance in 1618. Frederick I proclaimed himself king of Prussia in 1701. In 1871 William I became first emperor of Germany. The rule of the Hohenzollerns ended with Germany's defeat in World War I.

Prince Charles of the house of Hohenzollern-Sigmaringen, a branch of the Hohenzollern line, became King Carol I of Romania in 1881. The Hohenzollern-Sigmaringens reigned until 1947 when Romania ceased being a monarchy.