The Piabanha River () is a river of Rio de Janeiro state in southeastern Brazil. It is a tributary of the ParaÃÂba do Sul.
The basin of the Piabanha River includes the basins of the upper Piabanha, Preto, Fagundes and Paquequer rivers. It fully drains the municipalities of Teresópolis, Carmo, Sapucaia, Sumidouro, Areal and São José do Vale do Rio Preto, and partially drains the municipalities of Petrópolis, Paty do Alferes, ParaÃÂba do Sul, Duas Barras and Três Rios. The headwaters of the river are protected by the Três Picos State Park, Serra dos ÃÂrgãos National Park, Petrópolis Municipal Nature Park, Montanhas de Teresópolis Municipal Nature Park, Araras State Biological Reserve and Araponga Municipal Nature Park among others.
The Piabanha rises in Petrópolis and runs for to join the ParaÃÂba do Sul, passing through Areal and Três Rios. The Preto drains the municipalities of Teresópolis and São José do Vale do Rio Preto, and joins the Piabanha in Areal. The Piabanha also receives the Fagundes in Areal.