Two canoes crossing open water between forested points in the Boundary Waters

Updated August 2026

Biggest Inland Lake in Wisconsin: Lake Winnebago (137,708 acres)

Lake Winnebago is Wisconsin's largest inland lake per the Wisconsin DNR. Below: 50 Wisconsin lakes ranked by surface area.

The largest inland lake in Wisconsin is Lake Winnebago at 137,708 acres , in Winnebago, Calumet and Fond du Lac County, according to the Wisconsin DNR. Lake Michigan is larger at 22,300 sq mi water area, 925 ft max depth (US EPA). Great Lake shared with Michigan, Illinois and Indiana; Lake Superior also borders Wisconsin. Winnebago is the largest lake entirely inside the state.

See our Lake Winnebago water-quality readings —

Source: Wisconsin DNR (2009 (WI DNR PUB-FH-800 "Wisconsin Lakes"; retrieved 2026-07-30)). The table below ranks the Wisconsin lakes in our own index by surface area.

Lakes with area data

131,995

Largest (acres)

3,360

Median of top 50

14/50

Reservoirs (vs natural)

Reading Wisconsin's size profile

Wisconsin's largest lake by surface area is Lake Winnebago in Winnebago County, spanning 131,995 acres and reaching 21 ft deep. Most of Wisconsin's biggest waters are natural basins left by glaciers, with stable shorelines and deep main basins.

Surface area is a poor proxy for water quality on its own — a large lake can hold a clean, deep core and a nutrient-loaded bay at the same time. Each lake below links to its full page with nutrient readings, clarity, depth, and EPA impairment status. Area figures come from state DNR surveys and the USACE National Inventory of Dams; water-quality readings come from EPA and state monitoring data.

The 50 biggest lakes in Wisconsin by surface area

#	Lake	County	Surface area	Max depth
1	Lake Winnebago	Winnebago	131,995 acres	21 ft
2	Pepin Lake	Pepin	24,550 acres	60 ft
3	Petenwell Flowage Lake	Juneau	23,173 acres	44 ft
4	Lake Poygan	Winnebago	14,024 acres	11 ft
5	Turtle Flambeau Flowage Lake	Iron	13,798 acres	-
6	Castle Rock Lake	Juneau	12,991 acres	36 ft
7	Lake Koshkonong	Jefferson	10,595 acres	7 ft
8	Lake Onalaska	La Crosse	10,520 acres	40 ft
9	Lake Mendota	Dane	9,781 acres	83 ft
10	Lake Winneshiek	Crawford	8,992 acres	-
11	Lake Butte des Morts	Winnebago	8,581 acres	9 ft
12	Lake Dubay	Marathon	7,800 acres	-
13	Lake St Croix	St. Croix	7,696 acres	60 ft
14	Beaver Dam Lake	Dodge	6,542 acres	-
15	Big Eau Pleine Southeast Point Lake	Marathon	6,348 acres	46 ft
16	Shawano Lake	Shawano	6,215 acres	39.5 ft
17	Lac Courte Oreilles Lake	Sawyer	5,139 acres	90 ft
18	Lake Puckaway	Green Lake	5,013 acres	5 ft
19	Willow Reservoir	Oneida	4,880 acres	-
20	Lake Winneconne	Winnebago	4,553 acres	9 ft
21	Holcombe Flowage Lake	Chippewa	4,300 acres	-
22	Lac Vieux Desert Lake	Vilas	4,017 acres	38 ft
23	Trout Lake	Vilas	3,867 acres	117.1 ft
24	Tomahawk Lake	Oneida	3,578 acres	84 ft
25	Pelican Lake	Oneida	3,545 acres	39 ft
26	Lake Monona	Dane	3,360 acres	73.8 ft
27	Gile Flowage Lake	Iron	3,317 acres	-
28	Round Lake	Sawyer	3,294 acres	74 ft
29	Long Lake	Washburn	3,290 acres	-
30	Rainbow Flowage	Oneida	3,285 acres	28 ft
31	Lake Kegonsa	Dane	3,200 acres	32 ft
32	Grindstone Lake	Sawyer	3,176 acres	60 ft
33	North Twin Lake	Vilas	2,871 acres	60 ft
34	Rush Lake	Winnebago	2,729 acres	5 ft
35	Nelson Lake	Sawyer	2,717 acres	33 ft
36	Fox Lake	Dodge	2,713 acres	19 ft
37	Shell Lake	Washburn	2,513 acres	36 ft
38	Wisconsin River Flowage	Portage	2,491 acres	25 ft
39	Pewaukee Lake	Waukesha	2,437 acres	45 ft
40	Lake Chetac	Sawyer	2,400 acres	26 ft
41	Lake Noquebay	Marinette	2,398 acres	51 ft
42	Chequamegon Waters Flowage Lake	Taylor	2,366 acres	22 ft
43	Yellow Lake	Burnett	2,283 acres	31 ft
44	Saint Croix Flowage	Douglas	2,248 acres	28 ft
45	Muskego Lake	Waukesha	2,194 acres	23 ft
46	Buffalo Lake	Marquette	2,179 acres	8 ft
47	Lake Waubesa	Dane	2,074 acres	38 ft
48	Biron Flowage	Wood	2,066 acres	23 ft
49	Lake Metonga	Forest	2,038 acres	79 ft
50	Sinissippi Lake	Dodge	2,004 acres	8 ft

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Frequently Asked Questions

What is the largest lake in Wisconsin?

Lake Winnebago, at 137,708 acres, in Winnebago, Calumet and Fond du Lac County. Lake Michigan is larger at 22,300 sq mi water area, 925 ft max depth (US EPA). Great Lake shared with Michigan, Illinois and Indiana; Lake Superior also borders Wisconsin. Winnebago is the largest lake entirely inside the state. Source: Wisconsin DNR, 2009 (WI DNR PUB-FH-800 "Wisconsin Lakes"; retrieved 2026-07-30).

How is lake surface area measured?

Surface area comes from state DNR lake surveys and, for reservoirs, US Army Corps of Engineers (USACE) National Inventory of Dams records. Area is reported in acres at normal pool level. Reservoirs rise and fall with management and drought, so their listed area is the long-term normal rather than a single-day reading.

Are Wisconsin's largest lakes natural or reservoirs?

Of the top 50 Wisconsin lakes by area, 14 sit on a dammed river (reservoirs) and 36 are natural basins. Glacial states (MN, WI, MI, NY) skew natural; plains and southern states (MO, IA, ND, OH) skew toward reservoirs built for water supply, flood control, and recreation.

Do larger lakes have better water quality?

Not reliably. Quality varies more within a big lake than between lakes — a large lake can have a clean, deep main basin and a murky, algae-prone bay fed by a tributary, so one reading can mask wide swings. Depth, watershed land use, and how fast the lake flushes matter far more than raw surface area.

How big is the typical Wisconsin lake in this ranking?

Across the top 50 Wisconsin lakes by surface area, the median is 3,360 acres (Lake Monona). This list is biased toward the biggest waters; the typical Wisconsin lake is far smaller.

Where to stay near Wisconsin's largest lakes

Planning a trip? Jump to live cabin, resort, and hotel availability near Wisconsin's biggest lakes.

Deepest lakes in Wisconsin →Cleanest lakes in Wisconsin →Largest lakes (all states) →All Wisconsin lakes →