| Una River | |
| Source1 Location: | Rio de Janeiro state |
| Mouth: | Atlantic Ocean |
| Subdivision Type1: | Country |
| Subdivision Name1: | Brazil |
The Una River is a river of Rio de Janeiro state in southeastern Brazil. The river born of Araruama lagoon. It flows through fields north of Tamoios and São Pedro da Aldeia in the Baixadas mesoregion before it discharges into the Atlantic Ocean.