A supercargo (from Spanish sobrecargo) is a person employed on board a vessel by the owner of cargo carried on the ship. The duties of a supercargo are defined by admiralty law and include managing the cargo owner's trade, selling the merchandise in ports to which the vessel is sailing, and buying and receiving goods to be carried on the return voyage.
He has control of the cargo unless limited by his contract or other agreement. For instance, the supercargo has no authority over the stevedores, and he has no role in the necessary preparatory work prior to the handling of cargo. Because a supercargo sails from port to port with the vessel to which he is attached, he differs from a factor, who has a fixed place of residence at a port or other trading place.
During the Age of Sail from the 16th to the mid-19th century the supercargo was the second most important person aboard a merchant ship after the captain.
In 1818, Jean Laffite appointed Jao de la Porta supercargo for the Karankawa Indian trade.
On ships of the Swedish East India Company (1731–1813), the supercargo represented the company and was in charge of all matters related to trade while the captain was in charge of navigation, loading and unloading of cargo as well as the maintenance of the ship. In reality, the captain could do nothing without a written order from the supercargo. A new supercargo was always appointed for each journey who also had to keep books, notes and ledgers about everything that happened during the voyage and trade matters abroad. He was to present these immediately to the directors of the Company on the ship's return to its headquarters in Gothenburg. The supercargo received a heavy fine for each day the books were delayed. Helping him in all this he had a staff of assistants: a concierge, a cook, a footman and his own ship's court consisting of seven persons. According to historical documents, the court remained busy throughout the voyage. The supercargo also had to maintain and run the company's factory at the trading destination.
Having the highest rank aboard the ship, the supercargo also received the highest salary. In addition to this he received six percent of the value of the cargo the ship brought home. Every person on board had the right to buy, bring home goods and sell them back in Sweden. The amount of goods permitted was regulated by the person's rank aboard the ship and his financial means. At the top of this list was the supercargo.In Robert Louis Stevenson's Treasure Island, Long John Silver refers to the main character as having 'slept like a supercargo.'
In Alexandre Dumas, père's The Count of Monte Cristo, Danglars is supercargo of the ship of which Edmond becomes captain.
In Ian Fleming's Thunderball James Bond recalls that he was a supercargo on a submarine during World War II
In many of Louis Becke's Pacific Tales (1897), the supercargo Denison is the observer or hearer of the tale.
Myron Tany is the supercargo in Ports of Call by Jack Vance.
In the film, Captain Kidd and the Slave Girl, Eva Gabor is introduced to the supercargo and asks what he does; his role is explained to her.
In Anne McCaffrey’s Crystal Singer, Pendel is the supercargo aboard the Trundimoux Cruiser, who provides assistance to Heptite Guild Member Killashandra Ree.
In Flash for Freedom!, Harry Flashman is cajoled into being supercargo for his father in law to avoid a scandal.
In Voyager, Jamie Fraser becomes the supercargo for his cousin Jared's ship Artemis on the voyage from France to the West Indies to find Ian Murray, Jamie's nephew.
In the short story "Dagon" by H. P. Lovecraft the narrator of the tale is the supercargo of a packet during World War I and becomes stranded on an island in the Pacific following an attack by the Germans.