Alcácer do Sal is a municipality in Portugal with a total area of 1465.0 km² and a total population of 13,624 inhabitants. The city proper has a population of 6,602. The municipality is composed of 6 parishes, and is located in the district of Setúbal. The seat of the municipality is the city of Alcácer do Sal situated on the banks of the Sado River and with a population of 9,118 inhabitants. The present Mayor is Pedro Manuel Igrejas da Cunha Paredes (Socialist), who was elected after a long period of rule by the Portuguese Communist Party. The municipal holiday is June 24, the day of Saint John the Baptist. The first part of its name came from Arabic al qasr = "the castle". This name dates from the period when Muslims ruled most of Iberian Peninsula.