Lac Gregory is a body of fresh water crossed from north to south by the Tourilli River, located in the Laurentides Wildlife Reserve, in the unorganized territory of Lac-Croche, in the La Jacques-Cartier Regional County Municipality, administrative region of Capitale-Nationale, in province from Quebec, to Canada.
The watershed of Gregory Lake is served by a few secondary forest roads for the needs of forestry and recreational tourism activities.
Forestry is the main economic activity in the sector; recreational tourism, second.
The surface of Lake Gregory is generally frozen from the beginning of December to the end of March; safe circulation on the ice is generally done from the end of December to the beginning of March.
Lake Gregory has a length of , a width of and its surface is at an altitude of . This lake between the mountains is akin to the following three bays:
The mouth of Gregory Lake is located northeast of Tourilli Lake, west of the course of Jacques-Cartier River and north of the confluence of the Tourilli River and the Sainte-Anne River.
From the mouth of Gregory Lake, the current descends on generally towards the south, following the course of the Tourilli river to its confluence with the Sainte-Anne River; thence, the current generally flows south along the current of the Sainte-Anne river to the northeast bank of the Saint-Laurent river.
The toponym "Lac Gregory" was formalized on December 5, 1968, by the Commission de toponymie du Québec.