Secastilla (in Aragonese, Secastiella) is a municipality in the province of Huesca, in the autonomous community of Aragon, Spain. It is located in the northeastern part of the country, within the comarca of Ribagorza.
The municipality is sparsely populated, with a census-recorded population of 146 inhabitants in 2018. Its small size and rural setting are characteristic of many settlements in the Huesca province.