The Township of Enniskillen is located in the central region of Lambton County. The County of Lambton is located in southwestern Ontario, at the south end shores of Lake Huron. It is bounded on the west by the St. Clair River, and to the south by the parallel line of the northernmost tip of Walpole Island in Lake St. Clair. The northern boundary is the south shore of Lake Huron from Sarnia to the Ausable River (Grand Bend), which forms part of the eastern boundary separating Lambton from Middlesex County. ). The municipality presently surrounds the Town of Petrolia and the Village of Oil Springs. There are two hamlets located within the municipality, Marthaville and Oil City.