Mistassibi River
{{distinguish|Mistassini River}}
{{Infobox river
| name = Mistassibi River
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| image = Mistassibi-N-E%2C_Seuil_V%2C_km_138.jpg
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| subdivision_type1 = Country
| subdivision_name1 = Canada
| subdivision_type2 = Province
| subdivision_name2 = Quebec
| subdivision_type3 = Region
| subdivision_name3 = Saguenay–Lac-Saint-Jean
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| length_km = 298
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| source1 = Unnamed wilderness
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| source1_coordinates= {{coord|51|07|31|N|72|03|06|W|display=inline}}
| source1_elevation = {{convert|575|m|abbr=on}}
| mouth = Mistassini River
| mouth_location = Dolbeau-Mistassini
| mouth_coordinates = {{coord|48|53|04|N|72|13|05|W|display=inline,title}}
| mouth_elevation = {{convert|115|m|abbr=on}}
| progression =
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| basin_size_km2 = 9325
| tributaries_left = North-East Mistassibi River
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The Mistassibi River is a river in central Quebec, Canada. It is {{convert|298|km}} long and has a drainage basin of {{convert|9325|km2}}. Its source is an area with unnamed lakes about {{convert|50|km}} east of Canso Bay of Lake Albanel, eastern neighbor of Lake Mistassini.{{cite web |url=http://www.toponymie.gouv.qc.ca/ct/ToposWeb/fiche.aspx?no_seq=41524 |title=Rivière Mistassibi |publisher=Commission de toponymie du Québec |accessdate=2010-11-26 |language=French}}
The name Mistassibi, only in use since the late 19th century, comes from the Innu-aimun language, meaning "large river". Its alternate name used to be Rivière aux Foins (Hay River).
Just like the nearby Mistassini River, the Mistassibi River runs in a north–south direction. It passes through Lac au Foin (Hay Lake) and among its tributaries are the aux Oiseaux, du Dépôt, and North-East Mistassibi Rivers. It drains into the Mistassini River at Dolbeau-Mistassini.
The company Minashtuk Inc. operates a 12 MW run-of-the-river hydroelectric power station on the Mistassibi River since 2000.