Barragem de Poilão is a dam located in the eastern part of the island of Santiago, Cape Verde, in the municipality of São Lourenço dos Órgãos. It impounds the stream Ribeira Seca, the island's largest river. the reservoir, used for irrigation, stretches between the villages Poilão and Levada. North of the reservoir is the national road from João Teves to Achada Fazenda (EN1-ST03).