Marcilla is a town and municipality in the province and autonomous community of Navarre, in northern Spain. It is one of the many municipalities that make up this region of northern Spain, situated within the Ebro basin area of Navarre.
The municipality had a population of 2,821 inhabitants as of 2016. As a municipality, Marcilla covers both the town itself and the surrounding area under a single local administration, a common structure for towns of its size in Navarre.
Like other towns in the region, Marcilla is defined administratively as part of Navarre, which holds the status of an autonomous community within Spain. The town's modest population places it among the smaller municipalities of the province.