The Castle of Zafra (Spanish: Castillo de Zafra) is a 12th-century castle in the municipality of Campillo de Dueñas, in Guadalajara, Spain. Built in the late 12th or early 13th century on a sandstone outcrop in the Sierra de Caldereros, it stands on the site of a former Visigothic and Moorish fortification that fell into Christian hands in 1129. It had considerable strategic importance as a virtually impregnable defensive work on the border between Christian and Muslim-ruled territory.