The Connecticut Lakes are a group of lakes in Coos County, northern New Hampshire, United States, situated along the headwaters of the Connecticut River.
Third Connecticut Lake, at one time known as Lake St. Sophia, is a 93 ha water body in the town of Pittsburg, situated 32 km northeast of the village center, and less than 1.6 km south of the Canadian border. It reaches a maximum depth of approximately 30 m and sits 98 m higher in elevation than the second lake.
Fish species include rainbow trout and lake trout.
