The Paraibuna is a river in Minas Gerais state, Brazil, and a major tributary of the Paraíba do Sul.

The Paraibuna has its source near Antônio Carlos in the Serra da Mantiqueira at an elevation of 1,200 metres (3,900 ft).

It then flows northwest to southeast for 166 kilometres (103 mi) through the cities of Antônio Carlos, Santos Dumont, Ewbank da Câmara, Juiz de Fora, Matias Barbosa, Simão Pereira, Belmiro Braga, Santana do Deserto and Chiador before joining the Paraíba do Sul at an elevation of 250 metres (820 ft).

From its confluence with the Preto to its mouth on the Paraíba, it serves as the border between the states of Minas Gerais and Rio de Janeiro.

Along the valley of the Paraibuna were built the roads that opened up Minas Gerais and the Zona da Mata Mineira to settlement and development.