Lac Delaunay is the main body of fresh water at the head of the rivière du Sault Plat, flowing in the municipality of Rivière-au-Tonnerre, in the Minganie Regional County Municipality, in the administrative region of Côte-Nord, in province of Quebec, in Canada.

This toponym was entered in 1945 in the register of the Commission de géographie du Québec.

Delaunay arrived in Canada in 1635 to work as a clerk in the service of the Company of One Hundred Associates.

In 1645, the governor of Montmagny granted Delaunay land in the current Saint-Sacrement district of Quebec.

His surviving spouse remarried in 1655 to Vincent Poirier, sieur de Bellepoire; two daughters, Anne and Thérèse, were born from this second marriage.