CN Marine was a Canadian ferry company headquartered in Moncton, New Brunswick.

CN Marine was created by parent Canadian National Railway (CN) in 1977 as a means to group the company's ferry operations in eastern Canada into a separate operating division. The majority of these ferries also required federal subsidies to supplement fares, thus CN was unwilling to have the operating losses appear in the railway's accounts.

CN Marine undertook several major service improvements on the constitutionally-mandated services between Port Borden -Cape Tormentine and Channel-Port aux Basques-North Sydney by commissioning the construction of the new vessels Abegweit and Caribou in the late 1970s and early 1980s.

In 1986 the federal government renamed CN Marine to the current name Marine Atlantic. At that time, several vessels were retired, including the last rail ferries on the North Sydney-Port aux Basques route, in advance of the abandonment of railway services in Newfoundland in September 1987. Marine Atlantic itself made many changes a decade later, virtually decimating the remnants of CN Marine by removing itself from all routes and vessels except the constitutionally mandated service to Port aux Basques.