Karl Anton, Prince of Hohenzollern-Sigmaringen was the last prince of Hohenzollern-Sigmaringen before the territory was annexed by the Kingdom of Prussia in 1849. Afterwards he continued to be titular prince of his house and, with the death of the last prince of Hohenzollern-Hechingen in 1869, of the entire House of Hohenzollern. He served as Minister President of Prussia from 1858 to 1862, the only Hohenzollern prince to hold the post. His second son, Karl, became king of Romania. The offer of the throne of Spain to his eldest son, Leopold, was one of the causes of the Franco-Prussian War, which led to the unification of Germany and the creation of the German Empire.

Hohenzollern-Sigmaringen was a principality in southwestern Germany. Its rulers belonged to the senior Swabian branch of the House of Hohenzollern. The Swabian Hohenzollerns were elevated to princes in 1623. The small sovereign state with the capital city of Sigmaringen was annexed to the Kingdom of Prussia in 1850 following the abdication of its sovereign in the wake of the revolutions of 1848, then became part of the newly created Province of Hohenzollern.