Lac Courte Oreilles ( lə-KOO-də-ray) is a large freshwater lake located in northwest Wisconsin in Sawyer County in townships 39 and 40 north, ranges 8 and 9 west. It is irregular in shape, having numerous peninsulas and bays, and is approximately six miles long in a southwest to northeast direction and with a maximum width of about two miles (3 km). Lac Courte Oreilles is 5,039 acres (20.39 km²) in size with a maximum depth of 90 feet (27 m) and a shoreline of 25.4 miles (40.9 km). The lake has a small inlet stream (Grindstone Creek) that enters on the northeast shore of the lake and flows from Grindstone Lake, a short distance away to the north. An outlet on the southeast shore of the lake leads through a very short passage to Little Lac Courte Oreilles, then via the Couderay River to the Chippewa River, and ultimately to the Mississippi River at Lake Pepin.

Lac Courte Oreilles is located approximately eight and one-half miles southeast of the city of Hayward, the primary commercial and retail center of the area, and is one of three large natural lakes (Lac Courte Oreilles, Grindstone Lake, and Round Lake) located to the south and east of the city. There is a small unincorporated residential community on the north side of the lake commonly referred to as Northwoods (or North Woods) Beach. The eastern part of the lake is located in the Lac Courte Oreilles Indian Reservation. The shore of the lake is principally occupied by seasonal lake cabins and homes.

The lake has an abundance of northern pike, muskie, walleye, bass and other fish, and is a popular fishing destination. Lac Courte Oreilles is now a popular resort area drawing cabin owners and visitors from the Minneapolis-St. Paul, Milwaukee and Chicago metropolitan areas.