The Ischigualasto-Villa Unión Basin (Spanish: Cuenca de Ischigualasto-Villa Unión) is a small sedimentary basin located in the Argentine Northwest, Argentina. It is located in the southwestern part of La Rioja Province and the northeastern part of San Juan Province. The basin borders the Sierras Pampeanas in the east, the western boundary of the basin is formed by the , bordering the Precordillera, and it is bound in the southeast by the , separating the basin from the .