Zarzosa is a village and municipality in the province and autonomous community of La Rioja, in northern Spain. It is located within the Ebro Valley region of the country, in an area characterised by a sparse, rural population.
The municipality covers an area of 18.29 square kilometres (7.06 square miles). As of 2011, it had a population of 15 people, making it one of the smallest municipalities in La Rioja by number of inhabitants.