Illueca is a municipality in the province of Zaragoza, in the autonomous community of Aragon, Spain. It is located in the comarca of Aranda, in the western part of the province near the border with Castile and León.
According to the 2004 census (INE), the municipality had a population of 3,396 inhabitants. The town is known for its medieval castle, the Castillo de Illueca, a former residence of the Luna family, and as the birthplace of Pope Benedict XIII (Pedro de Luna), who was born there in 1328.