Lakes / Montana / Deepest Natural Lakes in Montana

Deepest Natural Lakes in Montana

Ranked by approximate maximum depth, from Washington Dept. of Ecology bathymetry. No exact published max depth exists for these lakes, so every depth here is a contour-based estimate and reads as About X ft. Only natural lakes are ranked - reservoirs and flowages are excluded.

#	Lake	County	Surface Area	Max Depth
1	Tally Lake	Flathead	1,211 acres	About 450 ft
2	Flathead Lake	Lake	122,132 acres	About 380 ft
3	Little Bitterroot Lake	Flathead	2,970 acres	About 260 ft
4	Saint Marys Lake	Lake	273 acres	About 240 ft
5	Sliderock Lake	Carbon	99 acres	About 225 ft
6	Whitefish Lake	Flathead	3,315 acres	About 220 ft
7	McGregor Lake	Flathead	1,522 acres	About 220 ft
8	Sanders Lake	Missoula	43 acres	About 210 ft
9	Ashley Lake	Flathead	2,850 acres	About 200 ft
10	Spar Lake	Lincoln	383 acres	About 200 ft
11	Sunburst Lake	Flathead	148 acres	About 200 ft
12	Courthouse Lake	Park	25 acres	About 200 ft
13	Lower Aero Lake	Park	187 acres	About 180 ft
14	Rainbow Lake	Carbon	89 acres	About 180 ft
15	Black Canyon Lake	Carbon	79 acres	About 180 ft
16	Lost Lake	Mineral	33 acres	About 180 ft
17	Lake of the Winds	Carbon	31 acres	About 180 ft
18	Upper Aero Lake	Park	228 acres	About 175 ft
19	Froze-to-Death Lake	Stillwater	69 acres	About 175 ft
20	Gibson Reservoir	Lewis and Clark	1,289 acres	About 165 ft
21	Middle Thompson Lake	Lincoln	557 acres	About 160 ft
22	Heart Lake	Mineral	60 acres	About 160 ft
23	Cliff Lake	Mineral	42 acres	About 160 ft
24	Lake Elwell	Liberty	14,842 acres	About 150 ft
25	Marion Lake	Flathead	69 acres	About 150 ft
26	Holland Lake	Missoula	414 acres	About 140 ft
27	Lower Thompson Lake	Lincoln	202 acres	About 140 ft
28	Crystal Lake	Lincoln	184 acres	About 140 ft
29	Fossil Lake	Carbon	133 acres	About 140 ft
30	Lake Elaine	Carbon	119 acres	About 140 ft
31	Lake Evangeline	Flathead	72 acres	About 140 ft
32	Albino Lake	Carbon	87 acres	About 135 ft
33	Horseshoe Lake	Lincoln	138 acres	About 130 ft
34	Goose Lake	Park	97 acres	About 130 ft
35	Big Lake	Missoula	37 acres	About 130 ft
36	Rock Tree Lake	Carbon	16 acres	About 130 ft
37	Swan Lake	Lake	3,269 acres	About 120 ft
38	Seeley Lake	Missoula	1,031 acres	About 120 ft
39	Lindbergh Lake	Missoula	815 acres	About 120 ft
40	Earthquake Lake	Madison	612 acres	About 120 ft
41	Foy Lake	Flathead	241 acres	About 120 ft
42	Cairn Lake	Carbon	116 acres	About 120 ft
43	Moon Lake	Carbon	79 acres	About 120 ft
44	Lightning Lake	Sweet Grass	55 acres	About 120 ft
45	Green Lake	Carbon	51 acres	About 120 ft
46	Black Lake	Flathead	49 acres	About 120 ft
47	Jorden Lake	Carbon	43 acres	About 120 ft
48	Medicine Lake	Carbon	37 acres	About 120 ft
49	Crystal Lake	Mineral	15 acres	About 120 ft
50	Loon Lake	Lincoln	222 acres	About 114 ft
51	Rough Lake	Park	90 acres	About 110 ft
52	Woodward Lake	Missoula	65 acres	About 110 ft
53	Little Arch Lake	Stillwater	50 acres	About 110 ft
54	Wildcat Lake	Flathead	38 acres	About 110 ft
55	Birch Lake	Flathead	29 acres	About 110 ft
56	Upper Thompson Lake	Lincoln	294 acres	About 100 ft
57	Widewater Lake	Carbon	166 acres	About 100 ft
58	Rock Island Lake	Park	156 acres	About 100 ft
59	Beaver Lake	Flathead	144 acres	About 100 ft
60	Murray Lake	Flathead	43 acres	About 100 ft
61	Lowary Lake	Carbon	26 acres	About 100 ft
62	Martin Lake	Carbon	24 acres	About 100 ft
63	Summit Lake	Carbon	22 acres	About 100 ft
64	Wrong Lake	Park	16 acres	About 100 ft
65	Marker Lake	Carbon	14 acres	About 100 ft
66	Placid Lake	Missoula	1,212 acres	About 93 ft
67	Clark Canyon Reservoir	Beaverhead	4,815 acres	About 91 ft
68	Lake Alva	Missoula	298 acres	About 90 ft
69	Boulder Lake	Missoula	109 acres	About 90 ft
70	Golden Lake	Carbon	58 acres	About 90 ft
71	Sodalite Lake	Park	27 acres	About 90 ft
72	Russell Lake	Carbon	24 acres	About 90 ft
73	Tendoy Lake	Beaverhead	21 acres	About 90 ft
74	Anchor Lake	Carbon	13 acres	About 90 ft
75	Cavity Lake	Park	10 acres	About 90 ft
76	Lion Lake	Flathead	39 acres	About 85 ft
77	Hebgen Lake	Gallatin	12,564 acres	About 80 ft
78	Canyon Lake	Carbon	62 acres	About 80 ft
79	Big Therriault Lake	Lincoln	56 acres	About 80 ft
80	Flat Rock Lake	Carbon	41 acres	About 80 ft
81	Upper Seymour Lake	Deer Lodge	40 acres	About 80 ft
82	Dewey Lake	Carbon	39 acres	About 80 ft
83	Crystal Lake	Carbon	34 acres	About 80 ft
84	Baldy Lake	Beaverhead	28 acres	About 80 ft
85	Lake of the Clouds	Carbon	26 acres	About 80 ft
86	Mirror Lake	Sweet Grass	23 acres	About 80 ft
87	Timberline Lake	Carbon	21 acres	About 80 ft
88	Leon Lake	Lincoln	19 acres	About 80 ft
89	Diamond Lake	Carbon	16 acres	About 80 ft
90	Rubble Lake	Missoula	15 acres	About 80 ft
91	Dude Lake	Carbon	14 acres	About 80 ft
92	Granite Lake	Carbon	14 acres	About 80 ft
93	Sienna Lake	Stillwater	13 acres	About 80 ft
94	Lake Pisce	Stillwater	8 acres	About 80 ft
95	Pishkun Reservoir	Teton	1,518 acres	About 78 ft
96	Lena Lake	Missoula	74 acres	About 75 ft
97	Margaret Lake	Flathead	46 acres	About 75 ft
98	Lake Inez	Missoula	288 acres	About 72 ft
99	Hidden Lake	Madison	147 acres	About 72 ft
100	Echo Lake	Flathead	695 acres	About 70 ft

Showing the top 100 of 508 counted lakes. Search above, or browse by county on the Montana page, for the full inventory.

Source: Washington Dept. of Ecology bathymetry (depths) and Washington DFW lake data. Verified October 30, 2026. New lakes are added as their records are verified - rankings update with every addition.