Castell-Castell was a county in the Holy Roman Empire, ruled by a branch of the Counts of Castell. It was established as a partition of Castell-Remlingen in 1668, and it was partitioned between itself and Castell in 1709. It annexed the County of Castell in 1772, and was mediatised to Bavaria in 1806.[1] On 7 March 1901 the Castell-Castell branch, along with the one of Castell-Rüdenhausen were raised to the hereditary rank of Prince in primogeniture with the style of Serene Highness by Luitpold, Prince Regent of Bavaria.[2]