Porto Velho is the capital of the Brazilian state of Rondônia, in the upper Amazon River basin. The population is about 334.661 people.

Located at the border of Rondônia and the state of Amazonas, the town is an important trade center of cassiterite, the mining of which represents the most important economic activity in the region, and a transportation and communication center. It is located on the eastern shore of the Madeira River, one of the main tributaries of the Amazon River.
The name Porto Velho means "Old Port"; the city grew around a port, at the banks of river Madeira.