Castell (/kæˈstɛl/ ka-STEL) is a small unincorporated, rural town in Llano County, Texas, United States.

Located in the heart of the Texas Hill Country, its northern border is formed by the Llano River.

It was part of a series of immigrant settlements sponsored by a group of prominent Germans known as the Adelsverein, including Baron Emil von Kriewitz,[4] John O. Meusebach, Prince Carl of Solms-Braunfels, Hermann Spiess, Gustav Schleicher, Ferdinand Ludwig Herff, and Count Carl Frederick Christion of Castell-Castell (1801–1850).

Castell has several small businesses, mainly centering on camping and hospitality as a result of the flyfishing and kayaking opportunities there.

[8] The climate in this area is characterized by hot, humid summers and generally mild to cool winters.