Piranhas River (disambiguation)

The Piranhas River or Açu River is a river of northeastern Brazil.

Piranhas River may also refer to:
 * Piranhas River (Goiás), in central Brazil
 * Piranhas River (lower Araguaia River tributary), in west-central Tocantins near Araguacema
 * Piranhas River (upper Araguaia River tributary), in northern Tocantins near Araguatins