There are 65 lakes known as Long Lake in Ontario, Canada.

Algoma

• Long Lake (Varley Township, Ontario)
• Long Lake (Albanel Township, Ontario)
• Long Lake (North Shore, Ontario)
• Long Lake (Fontaine Township, Ontario)
• Long Lake (Sampson Township, Ontario)
• Long Lake (Bruyere Township, Ontario)
• Long Lake (Common Township, Ontario)
• Long Lake (Huron Shores, Ontario)

Cochrane

• Long Lake (Timmins)
• Long Lake (Potter Township, Ontario)

Frontenac County

• Long Lake (South Frontenac, Ontario)
• Long Lake (Central Frontenac, Ontario)

Haliburton County

• Long Lake (Highlands East, Ontario)
• Long Lake (Dysart et al, Ontario)

Kenora

• Long Lake (Pelican Township, Ontario)
• Long Lake (Machin, Ontario)
• Long Lake (Kamungish River)
• Long Lake (Redvers Township, Ontario)
• Long Lake (Wabigoon River)

Manitoulin

• Long Lake (Central Manitoulin, Ontario)
• Long Lake (Northeastern Manitoulin and the Islands, Ontario)

Muskoka

• Long Lake (Bracebridge, Ontario)
• Long Lake (Wood Township, Ontario) (Muskoka Lakes)
• Long Lake (Cardwell Township, Ontario) (Muskoka Lakes)
• Long Lake (Bala, Ontario) (Muskoka Lakes)

Nipissing

• Long Lake (Kearney, Nipissing District, Ontario)
• Long Lake (East Ferris, Ontario)
• Long Lake (Calvin, Ontario)

Parry Sound

• Long Lake (Humphrey Township, Ontario) (Seguin)
• Long Lake (Kearney, Parry Sound District, Ontario)
• Long Lake (Joly, Ontario)
• Long Lake (East Mills Township, Ontario)
• Long Lake (Wilson Township, Ontario)
• Long Lake (Nipissing, Ontario)
• Long Lake (The Archipelago, Ontario)
• Long Lake (Foley Township, Ontario) (Seguin)

Peterborough County

• Long Lake (Douro-Dummer, Ontario)
• Long Lake (Havelock-Belmont-Methuen, Ontario)
• Long Lake (North Kawartha, Ontario)

Rainy River

• Long Lake (Rainy River District, Ontario)

Renfrew County

• Long Lake (Laurentian Valley, Ontario)
• Long Lake (Greater Madawaska, Ontario)
• Long Lake (Wylie Township, Ontario) (Laurentian Hills)
• Long Lake (Rolph Township, Ontario) (Laurentian Hills)

Sudbury

• Long Lake (Sables-Spanish Rivers, Ontario)
• Long Lake (Sudbury, Ontario) (Greater Sudbury)
• Long Lake (Ermatinger Township, Ontario)
• Long Lake (Capreol, Ontario) (Greater Sudbury)
• Long Lake (Kelly Township, Ontario)
• Long Lake (Turner Township, Ontario)

Timiskaming

• Long Lake (Sharpe Township, Ontario)
• Long Lake (Lorrain Township, Ontario)
• Long Lake (Milner Township, Ontario)
• Long Lake (Lebel Township, Ontario)

Thunder Bay

• Long Lake (Saganagons Lake)
• Long Lake (Laberge Township, Ontario)
• Long Lake (Kashabowie, Ontario)
• Long Lake (Terrace Bay, Ontario)
• Long Lake (Shuniah, Ontario)
• Long Lake (Athelstane Lake)
• Long Lake (Thunder Bay District) (Longlac, Ojibwe: Ginoogamaa-zaaga’igan)

Southern Ontario

• Long Lake (Lanark County)
• Long Lake (Simcoe County)
• Long Lake (Leeds and Grenville United Counties, Ontario)
• Long Lake (Kawartha Lakes)
• Long Lake (Hastings County)