Oligotrophic Lakes in Ontario

1573 oligotrophic lakes in Ontario. Low nutrients, clear water, excellent for swimming.

An oligotrophic lake is what most people picture when they think of pristine northern lake country: clarity to depth, no algal scum, cold water that holds dissolved oxygen all the way to the bottom even in August. Across Ontario, 1,573 lakes register as oligotrophic — 0% of them break 50 feet of depth, which is the structural condition that underwrites the trophic class. Without depth and a low-nutrient watershed, oligotrophy is hard to sustain.

On the LakeGrade rubric, oligotrophic lakes almost always pull an A or B — the same low-nutrient conditions that produce the trophic class also produce the high grade.

#	Lake	County	Grade	Clarity	Depth	TSI
1	Crosby Lake	Leeds and Grenville Counties	A	17.1 ft	-	37
2	Aird Lake	Renfrew	A	16.4 ft	-	37
3	Allen Lake	Haliburton	A	19.4 ft	-	31
4	Animoosh Lake	Nipissing District	A	15.6 ft	-	39
5	Anstruther Lake	Peterborough	A	16.4 ft	-	34
6	Apsey Lake	Sudbury District	A	-	-	36
7	Ardoch Lake	Frontenac	A	19 ft	-	33
8	Armishaw Lake	Parry Sound District	A	-	-	26
9	Armstrong Lake	Kenora District	A	16.1 ft	-	37
10	Armstrong Lake	Sudbury District	A	15.1 ft	-	34
11	Arnott Lake	Algoma District	A	24 ft	-	29
12	Arrow Lake	Thunder Bay District	A	24 ft	-	32
13	Ashby Lake	Lennox and Addington	A	18 ft	-	35
14	Aylen Lake	Nipissing District	A	17.9 ft	-	28
15	Bagot Long Lake	Renfrew	A	15.1 ft	-	40
16	Bass Lake	Leeds and Grenville Counties	A	19.4 ft	-	38
17	Bass Lake	Leeds and Grenville Counties	A	19 ft	-	33
18	Basshaunt Lake	Haliburton	A	15.7 ft	-	37
19	Basswood Lake	Algoma District	A	37.7 ft	-	22
20	Bay Lake	Hastings	A	21.2 ft	-	40
21	Bear Lake	Haliburton	A	19.4 ft	-	34
22	Bearhead Lake	Algoma District	A	17.1 ft	-	36
23	Beech Lake	Haliburton	A	15.9 ft	-	36
24	Bella Lake	Muskoka District	A	16.4 ft	-	35
25	Bells Lake	Parry Sound District	A	20 ft	-	32
26	Belmont Lake	Peterborough	A	17.1 ft	-	34
27	Big Barnum Lake	Haliburton	A	19.7 ft	-	31
28	Big Brother Lake	Haliburton	A	15.3 ft	-	34
29	Big Cedar Lake	Peterborough	A	16.4 ft	-	37
30	Big Clear Lake	Frontenac	A	15.1 ft	-	37
31	Big Clear Lake	Frontenac	A	21.3 ft	-	34
32	Big Hawk Lake	Haliburton	A	21.3 ft	-	30
33	Big Limestone Lake	Renfrew	A	16.4 ft	-	35
34	Big Olhman Lake	Frontenac	A	16.4 ft	-	39
35	Big Rideau Lake	Leeds and Grenville Counties	A	18.9 ft	-	36
36	Big Skunk Lake	Algoma District	A	15.7 ft	-	33
37	Big Straggle Lake	Haliburton	A	16.4 ft	-	35
38	Big Vermilion Lake	Sudbury District	A	19.7 ft	-	33
39	Billings Lake	Haliburton	A	18 ft	-	35
40	Bitter Lake	Haliburton	A	19 ft	-	32
41	Black Lake	Lanark	A	15.1 ft	-	38
42	Blackstone Lake	Parry Sound District	A	15.1 ft	-	37
43	Blue Lake	Parry Sound District	A	21.5 ft	-	28
44	Blue Lake	Nipissing District	A	25.4 ft	-	30
45	Blue Lake	Haliburton	A	22.3 ft	-	32
46	Blue Lake	Frontenac	A	37.7 ft	-	30
47	Blue Lake	Kenora District	A	17.1 ft	-	38
48	Bob Lake	Haliburton	A	15.1 ft	-	34
49	Bobs Lake	Frontenac	A	15.7 ft	-	37
50	Bonnie Lake	Muskoka District	A	19.7 ft	-	31
51	Boshkung Lake	Haliburton	A	18 ft	-	32
52	Bow Lake	Haliburton	A	26.2 ft	-	28
53	Brewster Lake	Renfrew	A	16.4 ft	-	38
54	Broder Lake	Sudbury District	A	16.4 ft	-	32
55	Brule Lake	Frontenac	A	23.3 ft	-	30
56	Buck Lake	Muskoka District	A	20.7 ft	-	34
57	Buckshot Lake	Frontenac	A	17.1 ft	-	33
58	Burchell Lake	Thunder Bay District	A	-	-	33
59	Burdock Lake	Haliburton	A	23 ft	-	33
60	Burns Lake	Renfrew	A	-	-	36
61	Burnt Lake	Parry Sound District	A	19.7 ft	-	32
62	Burridge Lake	Frontenac	A	17.2 ft	-	36
63	Buzzard Lake	Peterborough	A	20 ft	-	38
64	Camp Lake	Muskoka District	A	23 ft	-	31
65	Canonto Lake	Frontenac	A	20 ft	-	32
66	Carson Lake	Renfrew	A	20.3 ft	-	34
67	Cashel Lake	Hastings	A	17.6 ft	-	36
68	Chalk Lake	Durham Region	A	14.9 ft	-	37
69	Chandos Lake	Peterborough	A	16.4 ft	-	35
70	Chant Plain Lake	Nipissing District	A	-	-	34
71	Charleston Lake	Leeds and Grenville Counties	A	19.7 ft	-	36
72	Charlotte Lake	Renfrew	A	23 ft	-	32
73	Chiblow Lake	Algoma District	A	19.4 ft	-	28
74	Christie Lake	Lanark	A	15.1 ft	-	37
75	Clark Lake	Hastings	A	19.2 ft	-	31
76	Clean Lake	Haliburton	A	27.6 ft	-	28
77	Clear Lake	Muskoka District	A	21.3 ft	-	30
78	Clear Lake	Parry Sound District	A	23 ft	-	30
79	Clear Lake	Nipissing District	A	39.4 ft	-	23
80	Clear Lake	Haliburton	A	20.7 ft	-	29
81	Clear Lake	Parry Sound District	A	17.7 ft	-	32
82	Clearwater Lake	Muskoka District	A	18 ft	-	33
83	Clearwater Lake	Sudbury District	A	20.2 ft	-	34
84	Cliff Lake	Kenora District	A	-	-	36
85	Clinto Lake	Haliburton	A	24.6 ft	-	28
86	Cloudy Lake	Algoma District	A	19.4 ft	-	30
87	Coe Island Lake	Hastings	A	17.2 ft	-	36
88	Colton Lake	Renfrew	A	15.1 ft	-	34
89	Corine Lake	Algoma District	A	18 ft	-	31
90	Corkery Lake	Nipissing District	A	17.4 ft	-	34
91	Costello Lake	Nipissing District	A	40 ft	-	31
92	Crane Lake	Parry Sound District	A	15.7 ft	-	34
93	Cross Lake	Nipissing District	A	20.5 ft	-	30
94	Crow Lake	Frontenac	A	17.4 ft	-	34
95	Crown Lake	Haliburton	A	21 ft	-	32
96	Crystal Lake	Peterborough	A	16.4 ft	-	37
97	Crystal Lake	Rainy River District	A	17.4 ft	-	35
98	Cummings Lake	Algoma District	A	16.7 ft	-	30
99	Dam Lake	Renfrew	A	16.4 ft	-	36
100	Davern Lake	Lanark	A	17.1 ft	-	35

All oligotrophic lakes →Minnesota version →Wisconsin version →Illinois version →Michigan version →Iowa version →Ohio version →Pennsylvania version →New York version →Missouri version →Indiana version →North Dakota version →South Dakota version →Florida version →Colorado version →North Carolina version →Vermont version →Texas version →Oregon version →Arkansas version →Oklahoma version →Kansas version →Nebraska version →Nevada version →Arizona version →Idaho version →Montana version →New Mexico version →Tennessee version →Alabama version →Virginia version →Kentucky version →Utah version →Washington version →Wyoming version →Georgia version →Massachusetts version →Québec version →All Ontario lakes →

Source: EPA National Aquatic Resource Surveys, 2026.