Eastern Steamship Lines was a shipping company in the United States that operated from 1901 to 1955. It was created through successive mergers by Wall Street financier and speculator Charles W. Morse. The line sailed along the eastern seaboard of the United States and Canada, operating out of Boston and New York. Much of its fleet was sold Boston to the US government for use in World War I. After the war the company would order additional ships for the Post-war period. Eastern Steamship Lines served as operator for the War Shipping Administration in World War II. The United States government requisitioned all of the fleets vessels for military duty on both the Atlantic and Pacific.

Charles Wyman Morse was an American businessman and speculator who committed frauds and engaged in corrupt business practices. At one time he controlled 13 banks. Known as the "Ice King" early in his career out of New York City, through Tammany Hall corruption he established a monopoly in New York's ice business, before buying several shipping companies and moving into high finance. His attempt to manipulate the price of copper-shares set off a wave of selling that developed into the Panic of 1907. Jailed for violating federal banking laws, he faked serious illness and was released. Later he was indicted for war profiteering and fraud.