Alter do Chão is a municipality in the District of Portalegre in Portugal. The population in 2011 was 3,562, in an area of 362.07 km².The present Mayor is Joviano Martins Vitorino, elected by the Social Democratic Party. The municipal holiday is Ascension Day. The municipality is famous for its horsebreeding and high school of horseriding.ParishesAdministratively, the municipality is divided into 4 civil parishes: Alter do Chão Chancelaria Cunheira Seda