Caldas da Rainha is a medium-sized Portuguese city in the Oeste region, in the historical province of Estremadura, and in the district of Leiria. The city serves as the seat of the larger municipality of the same name and of the Comunidade Intermunicipal do Oeste. At the 2011 census, the municipality had a population of 51,729 in an area of 255.69 square kilometres, with 30,343 residing in the city.