Seagoing cowboys is a term used for men and ships used from 1945 to 1947 for United Nations Relief and Rehabilitation Administration and the Brethren Service Committee of the Church of the Brethren that sent livestock to war-torn countries. These seagoing cowboys made about 360 trips on 73 different ships. Most of the ships were converted World War II cargo ships with added cages and horse stalls. The Heifers for Relief project was started by the Church of the Brethren in 1942; in 1953 this became Heifer International. In the wake of the destruction caused by the Second World War, the historical peace churches in the United States (Church of the Brethren, the Society of Friends or "Quakers," and the Mennonites) sponsored relief missions to war-ravaged Europe, typically in cooperation with the United Nations Relief and Rehabilitation Administration (UNRRA). These relief missions usually took the form of transporting farm animals (such as heifers or horses), by transatlantic ship, to Poland and other countries where much of the livestock had been killed in the war. The men who tended the animals aboard these boats were called seagoing cowboys. These ships moved horses, heifers, and mules as well as chicks, rabbits, and goats. Ten seagoing cowboys died on the SS Park Victory when it sank after accidental grounding in the Gulf of Finland on December 25, 1947.

The Seagoing cowboys delivered to: Albania, China, Czechoslovakia (unloading in Bremen, Germany), Ethiopia, Greece, Italy, Poland, and Yugoslavia (unloading in Trieste, Italy). A total of 239,377 hoofed animals were transported. Over 7,000 men from the United States and Canada enlisted to be seagoing cowboys. Some 366 seagoing cowboys were from the Civilian Public Service.