Killer Lake is a lake in the Moira River and Lake Ontario drainage basins in Addington Highlands, Lennox and Addington County, Ontario, Canada. The lake is about 0.9 km long and 0.5 km wide and lies at an elevation of 328 m about 17 km east of the community of Gunter and 13 km northwest of the community of Cloyne. The primary inflow is Killer Creek at the northeast, and there is a secondary unnamed creek inflow at the northwest. The primary outflow, at the southeast, is also Killer Creek, whose waters flow via the Skootamatta River and the Moira River into the Bay of Quinte on Lake Ontario at Belleville.