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

Updated August 2026

Biggest Lake in Oregon: Upper Klamath Lake (61,543 acres)

Upper Klamath Lake is Oregon's largest lake per the Oregon Secretary of State — Oregon Blue Book (official state almanac). Below: 50 Oregon lakes ranked by surface area.

The largest lake in Oregon is Upper Klamath Lake at 61,543 acres , in Klamath County County, according to the Oregon Secretary of State — Oregon Blue Book (official state almanac).

Upper Klamath Lake isn't in our water-quality index — we grade lakes with enough EPA Water Quality Portal samples to score, which leaves out many large reservoirs and border waters. The ranking below covers the 50 Oregon lakes we do grade, led by Fremont Bridge Lake.

Source: Oregon Secretary of State — Oregon Blue Book (official state almanac) (2026-07-30). The table below ranks the Oregon lakes in our own index by surface area.

Lakes with area data

85,000

Largest (acres)

3,564

Median of top 50

19/50

Reservoirs (vs natural)

Reading Oregon's size profile

Oregon's largest lake by surface area is Fremont Bridge Lake in Klamath County, spanning 85,000 acres. Most of Oregon'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 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 50 biggest lakes in Oregon by surface area

#	Lake	County	Surface area	Max depth	Grade
1	Fremont Bridge Lake	Klamath	85,000 acres	-	D
2	Lake Umatilla	Morrow	50,042 acres	-	NR
3	Summer Lake	Lake	31,602 acres	-	NR
4	Harney Lake	Harney	31,290 acres	-	NR
5	Lake Bonneville	Wasco	19,452 acres	-	NR
6	Crater Lake	Klamath	13,211 acres	-	NR
7	Brownlee Reservoir	Baker	12,535 acres	-	NR
8	Wickiup Reservoir	Deschutes	11,330 acres	-	C
9	Silver Lake	Lake	10,452 acres	-	NR
10	Crump Lake	Lake	8,475 acres	-	NR
11	Mud Lake	Harney	7,922 acres	-	NR
12	Fern Ridge Lake	Lane	6,581 acres	-	NR
13	Bluejoint Lake	Lake	6,465 acres	-	NR
14	Waldo Lake	Lane	6,064 acres	-	NR
15	Crane Prairie Reservoir	Deschutes	4,940 acres	-	D
16	Drews Reservoir	Lake	4,694 acres	-	NR
17	Lookout Point Lake	Lane	4,086 acres	-	NR
18	Crescent Lake	Klamath	4,008 acres	-	A
19	Round Butte Dam Forebay Lake	Jefferson	4,000 acres	-	D
20	Gerber Reservoir	Klamath	3,812 acres	-	NR
21	Green Peter Lake	Linn	3,720 acres	-	A
22	Alvord Lake	Harney	3,648 acres	-	NR
23	Flagstaff Lake	Lake	3,633 acres	-	NR
24	Antelope Reservoir	Malheur	3,622 acres	-	NR
25	Siltcoos Lake	Lane	3,585 acres	-	D
26	Aspen Lake	Klamath	3,564 acres	-	NR
27	Detroit Lake	Marion	3,490 acres	-	B
28	Lost Creek Lake	Jackson	3,430 acres	-	C
29	Sturgeon Lake	Columbia	3,166 acres	-	NR
30	Prineville Reservoir	Crook	3,028 acres	-	D
31	Hills Creek Lake	Lane	2,592 acres	-	NR
32	Tahkenitch Lake	Douglas	2,325 acres	-	NR
33	Shallow Lake	Harney	2,305 acres	-	NR
34	Hells Canyon Reservoir	Wallowa	2,301 acres	-	NR
35	Campbell Lake	Lake	2,290 acres	-	NR
36	Phillips Lake	Baker	2,235 acres	-	NR
37	Thompson Reservoir	Lake	2,159 acres	-	NR
38	Howard Prairie Lake	Jackson	1,990 acres	-	D
39	Beulah Reservoir	Malheur	1,844 acres	-	NR
40	Fall Creek Lake	Lane	1,766 acres	-	NR
41	Dorena Lake	Lane	1,664 acres	-	NR
42	Cold Springs Reservoir	Umatilla	1,550 acres	-	F
43	Wallowa Lake	Wallowa	1,530 acres	-	A
44	Timothy Lake	Clackamas	1,430 acres	-	A
45	Paulina Lake	Deschutes	1,371 acres	-	NR
46	Coleman Lake	Lake	1,325 acres	-	NR
47	Cougar Lake	Lane	1,280 acres	-	A
48	Foster Lake	Linn	1,220 acres	-	C
49	Mckay Lake	Umatilla	1,200 acres	-	NR
50	Henry Hagg Lake	Washington	1,157 acres	-	A

Get updates on Oregon's largest lakes

New grades and algae readings on these waters as samples come in. Unsubscribe anytime.

Frequently Asked Questions

What is the largest lake in Oregon?

Upper Klamath Lake, at 61,543 acres, in Klamath County County. Source: Oregon Secretary of State — Oregon Blue Book (official state almanac), 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 Oregon's largest lakes natural or reservoirs?

Of the top 50 Oregon lakes by area, 19 sit on a dammed river (reservoirs) and 31 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 Oregon lake in this ranking?

Across the top 50 Oregon lakes by surface area, the median is 3,564 acres (Aspen Lake). This list is biased toward the biggest waters; the typical Oregon lake is far smaller.

Where to stay near Oregon's largest lakes

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

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