Lake Monomonac

Lake Monomonac
South end of Lake Monomonac
Location	Cheshire County, New Hampshire; Worcester County, Massachusetts
Coordinates	42°43′3″N 71°59′43″W / 42.71750°N 71.99528°W / 42.71750; -71.99528Coordinates: 42°43′3″N 71°59′43″W / 42.71750°N 71.99528°W / 42.71750; -71.99528
Primary inflows	North Branch Millers River
Primary outflows	North Branch Millers River
Basin countries	United States
Max. length	2.7 mi (4.3 km)
Max. width	0.7 mi (1.1 km)
Surface area	594 acres (2.4 km2)
Average depth	10 ft (3.0 m)
Max. depth	22 ft (6.7 m)
Surface elevation	1,045 feet (318.5 m)
Islands	Blueberry Island; Paradise Island
Settlements	Rindge, NH; Winchendon, MA

Lake Monomonac is an artificial lake that straddles the border between Rindge, New Hampshire, and Winchendon, Massachusetts, in the United States. It was created from a small pond in New Hampshire by the construction of dams on the North Branch of the Millers River, a part of the Connecticut River watershed.

Lake Monomonac is 594 acres (240 ha) in size with 411 acres (166 ha) in New Hampshire and the remaining 183 acres (74 ha) in Massachusetts. The lake has a maximum recorded depth of 22 feet (6.7 m) and an average depth of 10 feet (3.0 m).

The lake is classified as a warmwater fishery, with observed species including smallmouth and largemouth bass, black crappie, chain pickerel, white perch, pumpkinseed, bluegill, horned pout, and green sunfish.