Uncastillo (Aragonese: Uncastiello) is a municipality in the province of Zaragoza, Aragon, eastern Spain.

Along with Sos d'o Rei Catolico, Exeya d'os Caballers, Sádaba and Tauste, Uncastillo is one of the five towns comprising the comarca of Cinco Villas.

In 1966 Uncastillo was declared a Conjunto Histórico-Artístico.

Its other landmarks include the castle and palace of Peter IV (14th century).

This article about a location in the Province of Zaragoza is a stub.