Largest Lakes in Illinois

35 Illinois lakes with measured surface area, ranked by acreage. The biggest lake in Illinois is Carlyle Lake, which tops the list at 24,580 acres in Clinton County.

Lakes with area data

24,580

Largest (acres)

167

Median of top 35

35/35

Reservoirs (vs natural)

Reading Illinois's size profile

Illinois's largest lake by surface area is Carlyle Lake in Clinton County, spanning 24,580 acres. Most of Illinois's biggest waters are reservoirs — dammed river valleys built for water supply, flood control, and recreation, so their footprints shift with pool level.

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 report card with grade, clarity, depth, and EPA impairment status. Area figures come from state DNR surveys and the USACE National Inventory of Dams; grades come from EPA and state monitoring data.

The 35 biggest lakes in Illinois by surface area

#	Lake	County	Surface area	Max depth	Grade
1	Carlyle Lake	Clinton	24,580 acres	-	F
2	Lake Springfield	Sangamon	4,224 acres	-	F
3	Decatur Lake	Macon	3,335 acres	-	F
4	Kinkaid Lake	Jackson	2,500 acres	-	B
5	Lake of Egypt	Williamson	2,265 acres	-	C
6	Lou Yaeger Lake	Montgomery	1,410 acres	-	F
7	Mattoon Lake	Cumberland	980 acres	-	F
8	Governor Bond Lake	Bond	900 acres	-	F
9	Otter Lake	Macoupin	760 acres	-	D
10	Raccoon Lake	Marion	730 acres	-	F
11	Sara Lake	Effingham	586 acres	-	D
12	Jacksonville Lake	Morgan	477 acres	-	D
13	Holiday Shores Lake	Madison	345 acres	-	F
14	Centralia Lake	Marion	300 acres	-	D
15	Mauvaise Terre Lake	Morgan	262 acres	-	F
16	Round Lake	Lake	242 acres	-	B
17	Paradise Lake	Coles	174 acres	-	F
18	George Lake	Rock Island	167 acres	-	C
19	Kinmundy New Lake	Marion	100 acres	-	D
20	Glendale Lake	Pope	84 acres	-	B
21	Salem Lake	Marion	78 acres	-	F
22	Vienna Correctional Center Lake	Johnson	74 acres	-	C
23	Loch Lomond Lake	Lake	72 acres	-	A
24	Maple Lake	Cook	60 acres	-	D
25	Nashville City Lake	Washington	52 acres	-	F
26	Greenfield Lake	Greene	52 acres	-	D
27	Vernor Lake	Richland	45 acres	-	D
28	Palmyra-Modesto Lake	Macoupin	37 acres	-	C
29	Midlothian Lake	Cook	30 acres	-	D
30	One Horse Gap Lake	Pope	29 acres	-	B
31	Pounds Hollow Lake	Gallatin	28 acres	-	C
32	Fairfield Lake	Wayne	18 acres	-	F
33	Tecumseh Lake	Hardin	13 acres	-	B
34	Woods Creek Lake	McHenry	9 acres	-	C
35	Mermet Lake	Massac	1 acres	-	D

Frequently Asked Questions

What is the largest lake in Illinois?

The largest lake in Illinois in the LakeGrade dataset is Carlyle Lake in Clinton County at 24,580 acres. Water quality grade: F.

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 Illinois's largest lakes natural or reservoirs?

Of the top 35 Illinois lakes by area, 35 sit on a dammed river (reservoirs) and 0 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 grade 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 Illinois lake in this ranking?

Across the top 35 Illinois lakes by surface area, the median is 167 acres (George Lake). This list is biased toward the biggest waters; the typical Illinois lake is far smaller.

Where to stay near Illinois's largest lakes

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

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