Couillard made the announcement at the Port of Montreal and said his government's $9-billion maritime strategy is a major pillar of his plan to relaunch Quebec's economy and make Quebec the international point of entry into eastern North America.
The Liberals campaigned in 2014 on a $7-billion plan to boost maritime infrastructure but Couillard said his government realized after being elected there was more interest from the business community than originally thought.
He said he hopes $4 billion will come from private-sector companies looking to invest in projects along the St. Lawrence River relating to industries such as tourism, fishing and transportation.
A major part of the plan calls for the creation of a maritime transportation logistics hub in Contrecoeur, about 60 kilometres north of Montreal, and another one in Vaudreuil-Soulanges, just west of the city.
Couillard hopes the overall strategy will create 10,000 jobs within five years and 30,000 by 2030.
"Quebec has a unique opportunity to establish itself as the international door of entry into eastern North America with regard to goods and transit," he said.
What is currently unclear is what part the federal government will play in Quebec's maritime plan, as the country's ports fall under federal jurisdiction.
Moreover, Ottawa will likely have to balance a competing claim from Halifax, which also has an important maritime sector.
Ottawa announced more than $130 million in January for renovations at the Port of Montreal, which is expected to receive more traffic once the free-trade deal between Canada and the European Union is finalized.
Quebec's union of municipalities as well as the Canadian Federation of Independent Business welcomed Monday's announcement.