What's the longest river in the Patagonia?

Question

Surely it's located in the Argentinian side, but which river is the longest?

Answer 1

i think it might be the Futaleufu River -

The Futaleufu River is a river fed by the lakes in the Los Alerces National Park in Chubut Province, Argentina, crossing the Andes Mountains into Chile and opening into the Yelcho Lake.