Mullett Lake is a lake in Cheboygan County in the U.S. state of Michigan. The lake is named after John Mullett, who, together with William A. Burt, made a federal survey of the area from 1840 to 1843. A neighboring lake was named after Burt. Historically, Mullett Lake has been recorded as Mullet Lake, Mullet's Lake, and Mullett's Lake on maps and documents.
The lake is approximately 10 miles (16 km) long from southwest to northeast, about 4 miles (6.4 km) at its widest, and 120 feet (37 m) at its deepest. It covers 17,360 acres (70.3 km2), making it the third largest inland lake in Michigan.
Major inflows to the lake are the Indian River, which connects with nearby Burt Lake, Pigeon River, Little Pigeon River, Sturgeon River and Mullett Creek. The Cheboygan River flows out of the northeast end of the lake.
The lake is part of the great Inland Waterway, by which one can boat 38 miles (61 km) from Crooked Lake and Round Lake near the Little Traverse Bay of Lake Michigan across the northern tip of the lower peninsula's so-called mitten to Cheboygan on Lake Huron.
The Inland Waterway was a Native American trade route that was later opened to small steamer and modern recreational traffic.
I-75 passes to the west of the lake, with two interchanges near the south end of the lake at the unincorporated community of Indian River. M-27 passes along the northern shore of the lake through the unincorporated communities of Mullett Lake and Topinabee, while M-33 running north-south passes along a portion of the eastern shore through the community of Aloha.
Mullett Lake is an excellent fishery, containing large populations of game species, including brown trout, brook trout, rainbow trout, lake trout, splake, smelt, northern Pike, muskellunge, yellow perch, walleye, smallmouth bass, largemouth bass, and most notably lake sturgeon (the state record specimen was taken from these waters)