Daya Vieja is a municipality in the Valencian Community of Spain. It is located in the south-east of the Province of Alicante, within the comarca (district) of Vega Baja del Segura.
The town lies in the Vega Baja del Segura, a low-lying comarca in southern Alicante whose name refers to the fertile plain of the Segura river. Daya Vieja is one of the smaller municipalities of this district, which occupies the southern part of the province near the border with the Region of Murcia.
As a Valencian municipality, Daya Vieja forms part of the Valencian Community, one of Spain's seventeen autonomous communities, and falls administratively within the Province of Alicante.