Lac-Saint-Jean (French: [lak sɛ̃ ʒɑ̃], Quebec French pronunciation: [lak sẽ ʒã]) is a federal electoral district in the Saguenay–Lac-Saint-Jean region, northeast Quebec, Canada, that was represented in the House of Commons of Canada from 1925 to 2004, and has been represented since 2015.

Ethnocultural groups: 92% White, 6.9% Indigenous Languages: 98.5% French Religions: 83.3% Christian (76.3% Catholic), 16.2% No Religion Median income: $38,800 (2020) This riding was created in 1924 form parts of Chicoutimi—Saguenay riding and was originally named in English Lake St. John.

It was initially defined to consist of the county of Lake St. John East and the towns of Riverbend, Ile Maligne and St. Joseph-d'Alma; and parts of the county of Lake St. John West.

In 1996, it was redefined to consist of the towns of Alma, Desbiens and Métabetchouan; the County Regional Municipality of Lac-Saint-Jean-Est; and parts of in the County Regional Municipality of Le Fjord-du-Saguenay.

A by-election was held on October 23, 2017 due to the resignation of Denis Lebel on August 9, 2017.