Jorge Sampaoli (L) with Rennes sporting director Frederic Masssara ahead of a Ligue 1 loss to Toulouse. AFP
The 64-year-old, who has also coached Chile, Marseille and Sevilla, replaced Julien Stephan, fired last week.
Sampaoli watched Rennes lose at home to Toulouse on Sunday.
Last year, Rennes missed out on European qualification for the first time in seven campaigns. This season they are 13th in the 20-team table with three wins from 11 games.
"We're delighted that Jorge is joining us. He is a coach who is recognised internationally for his professionalism and humanism," said the club's executive chairman Arnaud Pouille in the statement.
"He has a strong attachment to his players and staff, and is a loyal and committed man. We need his energy to get the club moving again and to face the competition with determination."
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