| Lac-Frontière | |
| Pushpin Map: | Canada Southern Quebec |
| Pushpin Map Caption: | Location in province of Quebec. |
| Coordinates: | 46.7°N -70°W |
| Subdivision Type: | Country |
| Subdivision Type1: | Province |
| Subdivision Type2: | Region |
| Subdivision Name2: | Chaudière-Appalaches |
| Subdivision Type3: | RCM |
| Subdivision Name3: | Montmagny |
| Established Title1: | Constituted |
| Established Date1: | February 7, 1916 |
| Leader Title: | Mayor |
| Leader Name: | Guy Garant |
| Leader Title1: | Federal riding |
| Leader Name1: | Montmagny—L'Islet— Kamouraska—Rivière- du-Loup |
| Leader Title2: | Prov. riding |
| Leader Name2: | Côte-du-Sud |
| Area Total Km2: | 51.30 |
| Area Land Km2: | 50.47 |
| Population Total: | 198 |
| Population As Of: | 2011 |
| Population Density Km2: | 3.9 |
| Population Blank1 Title: | Pop 2006-2011 |
| Population Blank1: | 0.5% |
| Population Blank2 Title: | Dwellings |
| Population Blank2: | 169 |
| Timezone: | EST |
| Utc Offset: | −5 |
| Timezone Dst: | EDT |
| Utc Offset Dst: | −4 |
| Postal Code Type: | Postal code(s) |
| Postal Code: | G0R 1T0 |
| Area Code: | 418 and 581 |
| Blank Name: | Highways |
Lac-Frontière is a municipality in Montmagny Regional County Municipality within the Chaudière-Appalaches region of Quebec. It is located at the border (frontière in French) with the United States.