Encomienda de Víboras Castle, Medieval castle in Martos, Spain.

Encomienda de Víboras Castle is a medieval fortress in Martos that sits on elevated terrain with imposing defensive walls. The structure displays typical features of southern Spanish military architecture including crenellations, towers, and fortification systems.

The castle originated as a 9th-century Muslim fortification. Its name derives from Bib-Bora, Andalusian Arabic for "Gate of Bora", as it guarded the approach to the Turdetan city of Bora on Cerro de San Cristóbal, which minted coins around 50 BCE. After the Christian conquest it was granted in encomienda to the Order of Calatrava, who held it until the 19th-century Mendizábal ecclesiastical confiscation.

The name derives from Bib-Bora, Andalusian Arabic for "Gate of Bora", marking the access to the Turdetan city of Bora on Cerro de San Cristóbal, which minted coins around 50 BCE. After the Christian conquest the castle was granted in encomienda to the Order of Calatrava, who held it until the 19th-century Mendizábal ecclesiastical confiscation.

The castle stands on a promontory beside the Víboras river, next to the current reservoir, in the village of Las Casillas, about 10 km from Martos. Access is by road from Martos; the terrain around the hill is uneven, so wear sturdy shoes. The site has generic protection as a Spanish castle and is a Bien de Interés Cultural.

The name derives from Bib-Bora, Andalusian Arabic for "Gate of Bora", because the castle stood at the entrance to the Turdetan city of Bora on the Cerro de San Cristóbal, which minted coins around 50 BCE. The castle itself is first documented as a 9th-century construction.