Lake Bomoseen is a freshwater lake in the western part of the U.S. state of Vermont in the towns of Castleton and Hubbardton in Rutland County. It is the largest lake that lies entirely within the state's boundaries, with a surface area of approximately 2,400 acres (9.6 km2). The lake was formed by glaciation and has an average and maximum depth of 27 feet (8.2 m) and 65 feet (19.8 m), respectively. It drains a 24,770-acre (100.25 km2) watershed, has five major inlets, and empties to the Castleton River, a tributary of the Poultney River, which in turn flows west to East Bay at the southern end of Lake Champlain.

Vermont is a landlocked state in the New England region of the Northeastern United States. It borders Massachusetts to the south, New Hampshire to the east, New York to the west, and the Canadian province of Quebec to the north. As of the 2020 U.S. census, the state had a population of 643,503, ranking it the second least populated U.S. state ahead of Wyoming. It is the nation's sixth smallest state in area. The state's capital of Montpelier is the least populous U.S. state capital. No other U.S. state has a most populous city with fewer residents than Burlington. Vermont is also well known for being the largest producer of true maple syrup in the United States for over 200 years.