| Saint-Marc-du-Lac-Long | |
| Settlement Type: | Parish municipality |
| Pushpin Map: | Canada Eastern Quebec |
| Pushpin Map Caption: | Location in eastern Quebec |
| Coordinates: | 47.3944°N -68.8806°W |
| Subdivision Type: | Country |
| Subdivision Type1: | Province |
| Subdivision Type2: | Region |
| Subdivision Name2: | Bas-Saint-Laurent |
| Subdivision Type3: | RCM |
| Subdivision Name3: | Témiscouata |
| Established Title1: | Constituted |
| Established Date1: | June 11, 1938 |
| Leader Title: | Mayor |
| Leader Name: | Marcel Dubé |
| Leader Title1: | Federal riding |
| Leader Name1: | Rimouski-Neigette— Témiscouata—Les Basques |
| Leader Title2: | Prov. riding |
| Leader Name2: | Rivière-du-Loup-Témiscouata |
| Area Total Km2: | 155.90 |
| Area Land Km2: | 148.85 |
| Population Total: | 397 |
| Population As Of: | 2016 |
| Population Density Km2: | 2.7 |
| Population Blank1 Title: | Pop 2011-2016 |
| Population Blank1: | 9.8% |
| Population Blank2 Title: | Dwellings |
| Population Blank2: | 248 |
| Timezone: | EST |
| Utc Offset: | −5 |
| Timezone Dst: | EDT |
| Utc Offset Dst: | −4 |
| Postal Code Type: | Postal code(s) |
| Postal Code: | G0L 1T0 |
| Area Code: | 418 and 581 |
| Blank Name: | Highways |
Saint-Marc-du-Lac-Long is a parish municipality in the Canadian province of Quebec, located in the Témiscouata Regional County Municipality. It has a total area of 60.19 square miles, with a total land area of 57.47 square miles.
In the 2021 Census of Population conducted by Statistics Canada, Saint-Marc-du-Lac-Long had a population of living in of its total private dwellings, a change of from its 2016 population of . With a land area of 148.64km2, it had a population density of in 2021.[1]