The existence of this large lake was known to French explorers prior to its official discovery; Samuel de Champlain knew of it in 1603. It was finally discovered by Europeans in 1663 as part of an expedition ordered by Governor D'Avaugour and led by Guillaume Couture (first settler of Pointe-Lévy (Lévis) and hero of New-France). He was accompanied by Pierre Duquet and Jean Langlois, as well as by Native American guides; the whole group consisting of a fleet of 44 canoes. They went up the Saguenay River, reached Lake Mistassini and continued on the Rupert River which flows to the Hudson Bay.