| Champlain | |
| Settlement Type: | Regional county municipality |
| Coordinates: | 45.4833°N -102°W |
| Subdivision Type: | Country |
| Subdivision Type1: | Province |
| Subdivision Type2: | Region |
| Subdivision Name2: | Montérégie |
| Established Title: | Effective |
| Established Date: | January 1983 |
| Extinct Title: | Dissolved |
| Extinct Date: | December 31, 2001 |
| Seat Type: | County seat |
| Seat: | Longueuil |
| Government Type: | Prefecture |
| Area Total Km2: | 163 |
| Area Land Km2: | 169.64 |
| Area Note: | There is an apparent contradiction between two authoritative sources |
| Population Footnotes: | [1] |
| Population Total: | 311838 |
| Population As Of: | 2001 |
| Population Density Km2: | 1838.2 |
| Population Blank1 Title: | Change (1996–2001) |
| Population Blank1: | 0.8% |
| Population Blank2 Title: | Dwellings |
| Population Blank2: | 132367 |
| Timezone: | EST |
| Utc Offset: | −5 |
| Timezone Dst: | EDT |
| Utc Offset Dst: | −4 |
| Postal Code Type: | Postal code(s) |
| Area Code: | 450 |
Champlain was a former regional county municipality and census division in the Canadian province of Quebec. It ceased to exist when it amalgamated into the expanded city of Longueuil on January 1, 2002.
It was the smallest in area and most populous regional county municipality.
Champlain RCM consisted of:
On January 1, 2002, all of the above, plus Boucherville (formerly from Lajemmerais Regional County Municipality [now known as Marguerite-D'Youville Regional County Municipality]) and Saint-Bruno-de-Montarville (formerly from La Vallée-du-Richelieu Regional County Municipality), amalgamated into the expanded city of Longueuil. On January 1, 2006, however, Brossard, Boucherville, Saint-Bruno-de-Montarville, and Saint-Lambert demerged and became independent again; however, they remain part of the urban agglomeration of Longueuil.