| Guillaume-Alphonse Nantel | |
| Constituency Mp: | Terrebonne |
| Parliament: | Canadian |
| Predecessor: | Louis-Rodrigue Masson |
| Successor: | Joseph-Adolphe Chapleau |
| Term Start: | June 20, 1882 |
| Term End: | before August 16, 1882 |
| Office2: | Member of the Legislative Assembly of Quebec for Terrebonne |
| Predecessor2: | Joseph-Adolphe Chapleau |
| Successor2: | Jean Prévost |
| Term Start2: | 1882 |
| Term End2: | 1900 |
| Birth Date: | 4 November 1852 |
| Birth Place: | Saint-Jérôme, Canada East |
| Death Place: | Montreal, Quebec |
| Nationality: | Canadian |
| Party: | Conservative |
| Otherparty: | Conservative Party of Quebec |
| Relations: | Wilfrid Bruno Nantel, brother Antonin Nantel, brother |
Guillaume-Alphonse Nantel (November 4, 1852 - June 3, 1909) was a Canadian lawyer, journalist, author, newspaper owner, and politician. Born in Saint-Jerome, Canada East, he was elected to the House of Commons of Canada as a Conservative candidate in the Quebec riding of Terrebonne in the 1882 federal election. He resigned less than two months later to allow Joseph-Adolphe Chapleau, the Secretary of State of Canada, to run for office.
In an August 1882 by-election, he was acclaimed to the Legislative Assembly of Quebec in the riding of Terrebonne. He was re-elected in 1886 and 1890. He was acclaimed again in 1892 and re-elected in 1897. He was the commissioner of public works in the cabinets of Charles-Eugène Boucher de Boucherville and Louis-Olivier Taillon. He was also the commissioner of crown lands in the cabinet of Edmund James Flynn. He was defeated in the 1900 elections.
He died in Montreal in 1909. His brother, Wilfrid Bruno Nantel, was also a politician.