Lake Nicolet (in French: lac Nicolet) is located 50 km south of Victoriaville, in the municipality of Saints-Martyrs-Canadiens, in Arthabaska Regional County Municipality (MRC), in administrative region of Centre-du-Québec, Canada.

Lake Nicolet is the source of the Nicolet River which flows 137 kilometres (85 mi) to the southeast shore of lake Saint-Pierre, in Nicolet. The latest is crossed through the North-East by the St. Lawrence River.

This lake is surrounded by Chemin du Lac-Nicolet (north-west side) and Chemin Gosford-Sud (south-east side).

Lake Nicolet is 5.1 kilometres (3.2 mi) long and 1.7 kilometres (1.1 mi) wide, resembling a misshapen crescent surrounded by mountains. It has seven islands: Boulanger, Baril, Linke, L'Heureux, à Michel-Rheault, Rolland and a little unnamed island. The main mountain peaks around the lake are: Brûlé Mountain (500 metres (1,600 ft)) at 1.5 kilometres (0.93 mi) on the south side of the bay leading to the mouth of the lake; a 419 metres (1,375 ft) vertex on the west side and another on the southeast side (492 metres (1,614 ft)). This lake has a hundred chalets all around.

The toponym "Lac Nicolet" was made official on December 5, 1968, at the Commission de toponymie du Québec.

• Nicolet River
• Centre-du-Québec, administrative region