McKenzie Lake (French: lac McKenzie) is a lake in South Algonquin, Nipissing District and Hastings Highlands, Hastings County in Ontario, Canada.

[1][2][4][5][6] It is in the Saint Lawrence River drainage basin, is part of the Madawaska River river system, and lies about 14 kilometres (9 mi) south of the community of Madawaska and a similar distance north of the small town of Maynooth.

[2][5] The primary inflow is Moore Creek at the east, arriving from the direction of Cross Lake, with another unnamed inflow at the northwest; there are several other secondary unnamed inflows, including one at the south arriving from North Chainy Lake and another arriving at the northeast from Turf Lake.

It is roughly L-shaped, with the long axis running south-southwest to north-northeast, and the smaller extension running to about 1.5 kilometres (0.93 mi) to the south off the western end.

The lake is almost entirely in South Algonquin, Nipissing District, except for the southwestern tip, which is in Hastings Highlands, Hastings County, and thus straddles the traditional boundary between northern and southern Ontario, more specifically Nipissing District in Northeastern Ontario and Hastings County in Central Ontario.