| Guillaume Gamelin Gaucher | |
| Constituency Mp: | Jacques Cartier |
| Parliament: | Canadian |
| Predecessor: | Institution created in 1867 |
| Successor: | Rodolphe Laflamme |
| Term Start: | 1867 |
| Term End: | 1872 |
| Office2: | Member of the Legislative Assembly of the Province of Canada for Jacques-Cartier |
| Predecessor2: | François-Zéphirin Tassé |
| Successor2: | Institution abolished in 1866 |
| Term Start2: | 1864 |
| Term End2: | 1866 |
| Birth Date: | 16 August 1810 |
| Birth Place: | Sault-Saint-Louis (Kahnawake), Lower Canada |
| Death Place: | Sainte-Geneviève, Island of Montreal, Quebec |
| Party: | Conservative |
Guillaume Gamelin Gaucher (August 16, 1810 - September 16, 1885) was a Quebecois businessman and political figure. He represented Jacques-Cartier in the 1st Canadian Parliament as a Conservative member.
He was born Jean-Guillaume Gaucher in Sault-Saint-Louis (later (Kahnawake) in 1810 and was educated there. He became a merchant at Sainte-Geneviève on the Island of Montreal. Gaucher served as a lieutenant-colonel in the local militia and was also a justice of the peace. He was mayor of the parish of Sainte-Geneviève in 1845 and again from 1859 to 1863 after it became a village. He was elected to the Legislative Assembly of the Province of Canada for Jacques-Cartier in an 1864 by-election; he was elected again after Confederation.
He died at Sainte-Geneviève in 1885.