Castraz is a municipality in the province of Salamanca, in the autonomous community of Castile and León, western Spain. It lies about 67 kilometres (42 miles) from the city of Salamanca, the provincial capital.
The municipality covers an area of roughly 30 square kilometres (12 square miles) and sits at an elevation of about 760 metres (2,490 feet) above sea level. As of 2018, it had a population of only 42 people, making it one of the many sparsely populated rural settlements characteristic of this part of western Spain.