José Plácido de Castro (9 September 1873 – 11 August 1908) was a Brazilian soldier, surveyor, rubber producer and politician who led the armed revolt during the Acre War of 1902–03, when the Republic of Acre broke away from Bolivia.
He was the president of the state of Acre just before and after it was purchased by Brazil.
After the war he became extremely wealthy as a rubber producer, and made many enemies.