El Castillo del Bou Negre, also known as Castillo del Buey Negro, is a medieval Islamic fortification situated on a rocky plateau (muela) in the municipality of Argelita, province of Castellón. Its existence is documented from 1178, when it appears mentioned as a hisn (Arabic term for fortress) and as a boundary between the dioceses of Segorbe and Tortosa.

During the Andalusí period, the castle exercised dominion over an extensive territorial area that included numerous settlements in the region. It had a direct relationship with the Andalusí nucleus of Argelita, acting as a central element of control and defence of the territory. The structure was abandoned relatively soon after the Christian conquest, without developing any subsequent continuous occupation.

From a constructive standpoint, the castle is built in masonry, with a topographical ground plan adapted to the natural shape of the rocky plateau upon which it stands. Its structure is of a simple type, with only the remains of the former Islamic hisn preserved. The property is privately owned.

The castle was declared a Heritage Asset of Cultural Interest (BIC) with the category of monument on 25 June 1985, by decree, and was registered in the General Register of Heritage Assets of Cultural Interest of the Ministry of Culture with the code RI-51-0011124-00000. It is one of two BIC in the municipality of Argelita and one of 67 protected castles in Castellón province.

In its immediate surroundings are other outstanding heritage assets, such as the Fortified Church of Argelita, the Palace Castle of Ceyt Abu Ceyt and the Tower of Giraba. Access to the site is on foot from the urban centre of Argelita, following hiking routes that run through the characteristic landscape of Alto Mijares.