Lakes in Ontario

250,000inland lakes, the province’s stated count

Largest surface in the index

4,498.7 km²Lake Nipigon

Deepest contour in the index

124.4 mWanapitei Lake, a minimum

Deepest sounding in the index

92.5 mLake Joseph, 152,057 soundings

Most islands in the index

5,249Lake of the Woods, Ontario part

Lake Superior at its deepest

406 mthe deepest of the Great Lakes

How Many Lakes Are in Ontario?

The Government of Ontario gives the province’s count as 250,000 inland lakes, in addition to the Canadian portion of four of the Great Lakes. Elsewhere the province states the total as more than 250,000 lakes.

A count of lakes rests on a definition of a lake. The province’s map of surface water, the Ontario Hydro Network, classes every body of water by type, among them lake, pond, beaver pond, kettle lake and reservoir, so a pond and a lake are separate entries in it.

The rankings below cover the 265 lakes in the lake index. Each figure is read from the province’s own records: the surface, shoreline and islands from the Ontario Hydro Network’s outline of the lake, and the depth from the province’s bathymetry surveys.

The Largest Lakes in Ontario

Among the 265 lakes in the index, Lake Nipigon covers the largest surface, 4,498.7 square kilometers, followed by the Ontario part of Lake of the Woods at 2,194.4 and Lac Seul in Kenora District at 1,206.5.

The surface figure is the area of open water inside the lake’s outline, with its islands left out. Lake Muskoka covers 119.9 square kilometers of water, and the smallest lake in the index, Butterfly Lake, covers 0.6 square kilometers.

The Deepest Lakes in Ontario

Among the lakes in the index with a depth record, Wanapitei Lake in Sudbury District holds the deepest charted contour, 124.4 meters, and the water within it descends even farther. The deepest sounding in the index is on Lake Joseph in Muskoka, 92.5 meters.

Dryberry Lake at 103.6 meters and Dog Lake (Thunder Bay District) at 100.0 meters hold the next deepest contours. The Lake Joseph figure is determined from 152,057 soundings taken during Ontario’s 2003 survey. Charleston Lake at 92.0 meters and Lake Rosseau at 90.1 meters hold the next deepest soundings.

What Charted Depth Means

The province’s lake depths come from two kinds of record. A sounding is a depth measured at one point, and a depth contour is a line joining points of equal depth, drawn from soundings.

Sounding surveys. The province holds sounding records for 43 lakes in the index, 2,008,329 soundings between them, dated 1969 to 2018. The province’s record states that its soundings were taken mainly with an echo sounder positioned by GPS. On these lakes the depth figure is the deepest sounding, the maximum recorded depth.

Contour surveys. The province holds depth contours alone for 216 lakes in the index, 26,691 contours between them, dated 1955 to 2023 where a date is recorded. The province surveyed them to map fish habitat. On these lakes the depth figure is the deepest contour, the charted depth: the water inside that contour is deeper, by an amount the contour record does not state, so a charted depth is a minimum.

Six lakes in the index, among them Lake Nipigon and Lake of the Woods, hold no soundings and no depth contours in the province’s digital bathymetry records within their outlines, and have no depth in the rankings.

The Great Lakes on Ontario’s Border

Lake Superior, Lake Huron, Lake Erie and Lake Ontario border Ontario. Lake Superior is the largest and the deepest of the four, covering 82,100 square kilometers and reaching 406 meters.

Lake Huron, Georgian Bay included, covers 59,600 square kilometers and reaches 229 meters. Lake Ontario is the smallest of the four by surface, 18,960 square kilometers, and reaches 244 meters. Lake Erie is the shallowest, with a maximum depth of 64 meters and an average of 19.

Shoreline and Islands

The shoreline figure for each lake is the length of its mainland shore and of every island shore added together, and each is given with its two parts.

The Ontario part of Lake of the Woods has the longest shoreline in the index, 7,123 kilometers, and the most islands, 5,249. Of its shoreline, 2,568 kilometers is mainland shore and 4,555 the shore of its islands. Island shore makes up more than half the shoreline of the Ontario part of Lake of the Woods (64 percent), Stony Lake (56 percent), Newboro Lake (53 percent) and Lake Nipigon (53 percent).

Lake Muskoka has 451 kilometers of shoreline, 261 of it mainland shore and 190 the shore of its 220 islands. A shoreline figure that leaves the islands out, or that is measured on a coarser map, is shorter.

An island is counted at any size: every piece of land surrounded by the lake’s water in the provincial outline is one island. Eighteen lakes in the index hold no island, among them Lake Wolsey, Lake Doré and Drag Lake.

The Deepest and Largest Lakes by Region

In Muskoka, Lake Joseph holds the deepest record, 92.5 meters by sounding, and Lake Muskoka the largest surface, 119.9 square kilometers. In Haliburton County, Redstone Lake holds the deepest record, 80.5 meters by contour, and Kawagama Lake the largest surface, 31.6 square kilometers.

Common Questions