The Castle of Zafra (Spanish: Castillo de Zafra) is a 12th-century castle located in the municipality of Campillo de Dueñas, in Guadalajara, Spain. Built in the late 12th or early 13th centuries 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.

The castle was never conquered and was successfully defended against the King of Castile in the 13th century. The successful completion of the Reconquista at the end of the 15th century ended its military significance. Although it fell into ruin in the following centuries, since 1971 it has progressively been restored by its private owners. It can be visited with permission from the owners.