Castro Daire () is a municipality in Viseu District in Portugal. The population in 2011 was 15,339, in an area of 379.04 km<sup>2</sup>.
The present mayor is Paulo Almeida , elected by a coalition CDS-PP, PSD. The municipal holiday is June 29 (St Peter's Day).
Administratively, the municipality is divided into 12 civil parishes (freguesias):