Lake Truesdale is a lake located in the village of South Salem, New York. South Salem is in the town of Lewisboro in the northeast corner of Westchester County.
The lake is just under one mile (1.6 km) long and about 3/8 mile across at its widest point. The primary water flow into the lake comes from the swamp on Pumping Station Road in Ridgefield, Connecticut.
The 83.3-acre (337,000 m2) lake was created in 1927 by damming a stream and flooding a small pond and surrounding swamp. Two homeowners' associations (Truesdale Lake Property Owners' Association - TLPOA, and Truesdale Estates Association - TEA) manage the lake and maintain two beaches available to their members.