There are some hypotheses concerning the origin of the name of Montreal. The best-known is that it is a variant of "Mount Royal".
Historian Marcel Trudel asked: "Where does the name "Mount Royal" come from? In honour of Cardinal de Medici, Archbishop of Monreale? In honour of Claude de Pontbriand, son of the Seigneur of Montreal? Or simply in honour of the king? No explanation has been given." Claude de Pontbriand (landlord of the Château de Montréal in France) accompanied Jacques Cartier on his expedition up the Saint Lawrence River and was with him on October 3, 1535, when he reached Hochelaga, on the site of the present-day city of Montreal.
Among the hypotheses concerning the origin of Montreal's name, the most acceptable to Toponymy is the one that finds it to be a variant of Mount Royal. Note that in the 16th century réal was a variant of royal, hence the contraction of Mont Royal that gave Mont Réal or Montreal, as we have it today.
The name Montreal referred first to the mountain, then to the island and finally to the city itself.
The original name for the settlement that would later become Montreal was Ville-Marie. When the missionary society Société Notre-Dame de Montréal sent Paul Chomedey de Maisonneuve to found a city on the island of Montreal in 1642, they named the settlement Ville-Marie in honour of the Virgin, protectress of the venture. Nonetheless, from the very beginning both the settlement of Ville-Marie and the mountain were known as Montreal to many people, including some mapmakers of the period. In the 18th century, for no official reason, the name Montreal supplanted that of Ville-Marie. Up until then, the city was called either Montreal and/or Ville-Marie.