The creation of the Saguenay–St. Lawrence Marine Park (Québec, Canada) was the result of a long and sometimes difficult process involving local communities and regional stakeholders, Aboriginal communities, and the governments of Québec and Canada. This paper describes the very first proposals for a conservation park in the Saguenay region; citizen involvement in the protection of the beluga whale (Delphinapterus leucas) population; inter-governmental negotiations; public consultations on the territorial limits of the park; and the adoption of mirror laws leading to the establishment of a marine park with a total area of 1245 km2. This park covers a large part of the Saguenay Fjord and the northern section of the St. Lawrence Estuary between Gros cap à l’Aigle and Les Escoumins. Constantly renewed support from local communities and political bodies has meant that what was seen as a utopia in the early 1970s, has become, 45 years later, a tangible reality, contributing to the conservation of a large and highly disturbed marine area.