Castrillo de Cabrera (Castriellu de Cabreira in Leonese) is a municipality in the province of León, in the autonomous community of Castile and León, Spain. It lies in the mountainous northwest of the province, within the traditional Leonese-speaking area known as Cabrera.
The municipality is made up of six villages: Castrillo de Cabrera, which serves as the municipal seat, along with Marrubio (Manrubiu), Noceda de Cabrera, Nogar (Ñugare), Odollo (Udoyu) and Saceda (Saceda). Several of these villages are also known by their Leonese forms.
According to the 2010 census (INE), the municipality had a population of 152 inhabitants spread across those six villages, reflecting the small, dispersed settlement pattern typical of this part of rural León.