County in the Holy Roman Empire, in Franconia in central Germany (the castle is east of Kitzingen, ESE of Würzburg and SSE of Schweinfurt).
The Noble Lords of Castell became Counts in 1205, and divided into two lines in the 1260s until 1331 and again in 1597. The two 1597 lines were those of Rüdenhausen (extinct in 1803) and Remlingen, which itself divided into several lines in 1736, only one of which, Castell-Castell, survived by 1773. Castell-Castell itself divided into two lines, one of which later took the name of Castell-Rüdenhausen.
The Castell lands were mediatised in 1806, becoming part of Bavaria. Most of them were transferred to the Grand Duchy of Würzburg in 1810, returning to Bavaria in 1815.
The Counts belonged to the Franconian Imperial Circle (and in the Imperial Diet to the Franconian Gräfenbank). The heads of the two lines, Castell-Castell and Castell-Rüdenhausen, became Bavarian Princes in 1901.