Monroe Lake is a reservoir located about 10 miles (16 km) southeast of Bloomington, Indiana, United States. The lake is the largest entirely situated in Indiana with 10,750 acres (43.5 km2) of water surface area spread over the counties of Monroe and Brown. Capacity varies from 292 gigalitres (237,000 acre⋅ft) to 428 gigalitres (347,000 acre⋅ft) depending on water level. It is also home to 13,202 acres (53.43 km2) of protected forest and three recreational areas (Fairfax, Hardin Ridge, and Paynetown). Indiana's only federally protected U.S. Wilderness Area, the 13,000-acre (53 km2) Charles C. Deam Wilderness Area, is located on the south shore. The lake's watershed is 441 square miles, 82% of which is forested or farmland. The pool elevation (above sea level) is about 538 feet (164 m) year-round. During colder winters, limited ice fishing is available on protected backwater portions of the reservoir.
Ransburg Scout Reservation, a large Boy Scout camp comprising over 624 acres (253 ha), is situated along the eastern shore with a private dock system in Siscoe Bay (also known as Boy Scout Bay). The largest marina situated on the lake is the Fourwinds Resort and Marina with over 800 boats. The reservoir provides abundant fishing throughout the year, and recreational opportunities such as boating and water skiing attract visitors from throughout Indiana and the Midwest.