In 1947, some of the companies in charge of Finnish imports and exports, under the direction of the state-owned forest industry, established a shipping company called Merivienti Oy to handle sea transports to the United States. Its subsidiary was Oy Finnlines Ltd.

Six second-hand steamers were purchased the same year; the largest one, SS Tornator, came from Denmark and began operating in February 1948, crossing the Atlantic with a load of 5,667 tons of pulp and paper.

SS Tornator (1947-1954)
6,800 DWT,
speed 9.5 knots.
Purchased from Denmark, where it had been built in 1916.

The vessels were too old, however, to cope with the country's transport demands. The company's first newbuilding was completed in the Netherlands in 1951, and a series of three vessels - MS Finntrader , MS Finnpulp and MS Finnsailor - began operating in 1953. The old steamers were decommissioned from Atlantic routes as part of the construction programme. Once MS Finnmerchant and MS Finnboard had begun operating in 1956 and 1958 respectively, Finnlines had a fleet of seven vessels and offered weekly departures to the US. In 1960 the fleet was extended with the new and powerful MS Finneagle, MS Finnclipper and MS Finnforest.

MS Finntrader (I) (1951-1970)
6,435 DWT,
12 passenger berths,
speed 15 knots.
Built in the Netherlands.

MS Finnclipper (I) (1962-1978)
11,200 DWT,
speed 16 knots.
Built in Germany.

Until the early 1960s, all car and lorry traffic from Finland to Central Europe had to go through Sweden. The first icestrengthened ferry HansaExpress was ordered in 1962 and began operating between Hanko (Finland) and Travemünde (Germany) via Gotland (Sweden). Right from the beginning it was apparent that the vessel was too small and it was lengthened the following winter, increas- ing passenger capacity from 133 to 179 berths. Hanko was also found to be too small and too distant, so in 1963 the route was changed to Helsinki-Kalmar-Travemünde.

The first passenger ferries built in Finland, Finnhansa and Finnpartner, began operating in 1966 on the Hansa route (Helsinki-Travemünde). In addition to transporting passengers, the vessels offered an excellent alternative to lorry traffic between Finland and Germany.

MS Finnhansa (I) (1966-1978)
Passenger ferry
2,510 DWT,
1,700 passenger berths,
speed 20 knots.
Built in Finland.

As passenger traffic was limited to the summer season, the expensive car ferries must at other times be put to effective use in cargo transports. This, however, required swift loading and unloading procedures, which led to Finnlines developing its own Finnflow cargo handling system on wheels. This in turn caused the development of new kinds of ro-ro vessels, the prototype being MS Finncarrier, built in 1969. Its sister vessels, MS Hans Gutzeit and MS Finnfellow, included slight improvements in design and were completed in 1972-73.

MS Finncarrier (1969-1975)
Ro-ro/passenger vessel
1,000 lane metres,
36 passenger berths,
speed 18 knots.
Built in Finland.

In the early 1980s, Finnlines designed the new-generation "jumbo ro-ro" vessels MS Arcturus, MS Finnmerchant and MS Oihonna for traffic to Britain. Later the same design was adopted for the Baltic fleet in the form of MS Finnsailor and MS Antares.

Finnjet, a new kind of gas turbine vessel, was built in the mid-1970s for passenger traffic. The original aim was that the ship would travel between Helsinki and Travemünde in 22 hours at a speed of 30 knots. The oil crisis affected the vessel's cost-effectiveness, and diesel engines were added to it for use in quieter periods. Finnlines' passenger traffic in the Baltic Sea ended in 1986, when Enso-Gutzeit sold the Finnjet to Effoa.

Just before the recession in the early 1990s, Finnlines invested in three new "combi ro-ro" vessels - MS Finnhansa, MS Finnpartner and MS Finntrader - built in Poland. Each have a capacity of 3,200 lane metres and 114 passenger berths. Together with MS Transeuropa, which was ordered later, these vessels began operating between Finland and Germany in 1994- 1995.

MS Finnhansa (II) (1994- )
Combi ro-ro
3,200 lane metres,
114 passenger berths,
speed 20 knots.
Built in Poland.

In the late 1990s the company commissioned two new ro-pax (roro/passenger) vessels with capacity for over four hundred passengers. These vessels, MS Finnclipper and MS Finneagle, were joined in 2003 by sister vessel MS Finnfellow.

MS Finnclipper (II) (1999- )
Ro-pax vessel
2,500 lane metres,
440 passenger berths,
speed 21 knots.
Built in Spain.

In 2004, Finnlines ordered five new-generation ro-pax vessels from the Italian shipbuilder Fincantieri. These will be the largest ro-pax vessels ever built, and the fastest in their size class. Each vessel's cargo capacity will be 4,200 lane metres and they will have room for 500 passengers. They will travel at a speed of 25 knots. Three of the new ro-pax vessels will be placed on Finnlines' Finland-Germany route, while two will operate in Sweden related routes.

In 2007 after the delivery of all new vessels Finnlines will have a multi-purpose fleet of some 80 vessels. 17 of these will be ropax vessels especially designed into the Baltic circumstances.