The Supreme Court in Chile has ruled in favour of a dam project in Patagonia, in the south of the country.
The court rejected an appeal by environmental groups who fear it will damage Patagonia's fragile ecosystem.
The project is a joint venture by the Endesa energy company of Spain and Colbun of Chile.
It will involve the building of five dams on two rivers - two on the river Baker and three on the river Pascua. About 6000 hectares of land would be flooded.
The government says the dams are essential to meet Chile's growing energy needs.
A lower court also found in favour of the project in October 2011.
Environmental groups appealed against that decision, taking it to the Supreme Court.
Wednesday's ruling was the last legal hurdle in the way of the project.
Construction work could begin in 2014 and is expected to take around 10 years.
A 2000km transmission line will also be built to carry power to the capital, Santiago.