Saint-Nazaire-de-Dorchester is a parish municipality of 400 people in the Bellechasse Regional County Municipality, Quebec, part of the Chaudière-Appalaches administrative region. It is the least populous municipality in Bellechasse.
In the 2021 Census of Population conducted by Statistics Canada, Saint-Nazaire-de-Dorchester had a population of living in of its total private dwellings, a change of from its 2016 population of . With a land area of , it had a population density of in 2021.