For the former Saint-Prosper in Mauricie, see Saint-Prosper-de-Champlain, Quebec.Saint-Prosper is a municipality in Les Etchemins Regional County Municipality in Quebec, Canada. It is part of the Chaudière-Appalaches region and the population is 3,617 as of 2009. It is named after Reverend Prosper-Marcel Meunier, first priest of the parish. It is sometimes known as Saint-Prosper-de-Dorchester.