Forte de Santo António da Barra (also known as Santo António do Estoril Fort, Old Fort or Salazar Fort) is located overlooking the sea in the parish of Cascais and Estoril, in the village of São João do Estoril, Cascais municipality, Lisbon district, in Portugal. It is considered the main fortification between the Citadel of Cascais and the Fort of São Julião da Barra.