Casimiro de Abreu (Portuguese pronunciation: [ˌkaziˈmiɾu dʒi.aˈbɾeu̯]) (formerly known as Barra de São João Portuguese pronunciation: [ˈbaxɐ dʒiˈ sɐ̃w ʒuɐ̃w]) is a municipality located in the Brazilian state of Rio de Janeiro. Its population was 26,243 (2005) and its area is 461 km².