Seia is a municipality in Guarda District in Portugal. The population in 2011 was 24,702, in an area of 435.69 km². Its urban population is about 7,000. Seia was elevated to city status on July 3, 1986.
The municipality is situated on the northwestern slope of Serra da Estrela, the highest mountain range in mainland Portugal, with a top height of 1993 meters.
The present Mayor is Carlos Filipe Camelo, elected by the Socialist Party. The municipal holiday is July 3.
Seia has an annual cinema festival called CineEco that focuses on films with ecological and natural themes.