The O'Sullivan River flows North into the Abitibi Regional County Municipality, and into Eeyou Istchee James Bay (municipality), in the Nord-du-Québec, in Quebec, in Canada.

The course of the O'Sullivan River crosses the townships of Charrette, Adhémar, Labrie, Ralleau, Ruette, Benoit, Duplessis and Bossé.

From the small head lake, the O'Sullivan River flows over: The natives used the name "Pusticamica" to designate this watercourse.

At the request of the Commission de toponymie du Canada, the name "Rivière O'Sullivan" has been attributed to evoke the work of life of Henry O'Sullivan (Sainte-Catherine-de-Fossambault], 1845 - Loretteville, 1912).

[2][3][4] The toponym O'Sullivan River was formalized on December 5, 1968, at the Bank of Place Names of the Commission de toponymie du Québec.