Gdynia-America Shipping Lines S.A. (Gdynia America Line - GAL) was a Polish-Danish joint stock company based in Gdynia, established in 1930 under the name of the Polish Transatlantic Shipping Company Limited (PTTO) in order to mark the Polish presence on the Atlantic; in 1934 transformed into Gdynia-America Shipping Lines.The Danish owners became eager to sell their interests, as in 1931 the United States authorities severely reduced immigrant quotas and the line was threatened with bankruptcy. The Polish owners renamed the company Polskie Transatlantyckie Towarzystwo Okrętowe (Polish Transatlantic Shipping Company Limited or PTTO)The line added routes, particularly to South America, with its River Plate Service.

PLO was founded as a state owned company in 1951, with the merger of: Gdynia-Ameryka Linie Żeglugowe S.A. (Gdynia-America Line – GAL), Żegluga Polska (Shipping Polish) and Polsko-Brytyjskie Towarzystwo Okrętowe (Polish-British Shipping Partnership). After the creation of the company there was gradual development including buying more equipment and increased employment.