The Opémisca River is a tributary of the Chibougamau River, flowing into the regional County Municipality (RCM) of Eeyou Istchee Baie-James, within the administrative region of Nord-du-Québec, province of Quebec, Canada.

The hydrographic slope of the Opémisca River is accessible by a forest road on the North shore of Opémisca Lake and connecting South to route 113 which connects Lebel-sur-Quévillon to Chibougamau and passes South of the lake.

The surface of the Opémisca River is usually frozen from early November to mid-May, however, safe ice circulation is generally from mid-November to mid-April.

The Opémisca River originates from a forest stream (elevation: 358 metres (1,175 ft)) in the Cuvier township.

The latter is crossed to the northwest by the Waswanipi River which is a tributary of Matagami Lake.