Castellfort is a municipality in the province of Castellón, within the Valencian Community of eastern Spain. It lies in the mountainous comarca of Els Ports, a largely rural and sparsely populated area in the province's interior.
The municipality has a population of approximately 238 people, making it one of the smaller settlements in the region. Its location in the Els Ports highlands places it within a rugged, mountainous landscape characteristic of that part of Castellón.