The Peribonka River springs a short distance west of the Otish Mountains in a swampy area on the granite and muskeg of the Canadian Shield. From there it flows south until Lamarche, forming the boundary between the Maria-Chapdelaine and Le Fjord-du-Saguenay Regional Counties. From Lamarche, it flows west to Lac Saint-Jean. Its basin of comprises about one-third of the entire Saguenay River basin.