Fontellas is a town and municipality in the province and autonomous community of Navarre, in northern Spain. It lies within the Ebro basin of Navarre, a region of the country's north-east that borders the Basque Country, La Rioja and Aragon.
The municipality is linked to the Marquisate of Fontellas, a Spanish noble title associated with the town. This connection is among the settlement's notable historical characteristics.