Rio Branco is a major river flowing through Roraima state in northern Brazil.

It forms near Boa Vista at the confluence of the Rio Uraricoera, which rises in the Serra Parima along the Venezuela border, and the Rio Takutu, descending from the Serra Pakaraima on the Guyana border.

From there it runs south-southwesterly approximately 775 km before joining the Rio Negro, itself a principal tributary of the Amazon. The lower stretches of Rio Branco are navigable, but the upper course is interrupted by numerous rapids.

During dry seasons, water levels drop significantly, complicating travel between Boa Vista and the Rio Negro. The 1. 2-kilometer Macuxi Bridge spans the river within Boa Vista, offering a notable landmark along its banks.