Thorvald Nilsen (6 August 1881 – 19 April 1940) was captain of the polar ship, the Fram and deputy commander during Roald Amundsen's expedition to Antarctica (1910–12).

At the request of Fridtjof Nansen, oceanographic measurements and observations were now to be made in the relatively unexplored southern Atlantic Ocean.

Nilsen discovered that nothing had been arranged for this part of the expedition, but the financial problems were solved with the help of the relocated Norwegian businessman Don Pedro Christophersen.

The intention was now to embark on the North Pole voyage, and Nilsen stayed in Buenos Aires to take care of the equipment and the reparation of the Fram.

It has been claimed that he had a close relationship with Don Pedro's daughter Carmenzia, but Nilsen's reserved nature and a certain "difference in status" may indicate that this was not the case.

Thorvald Nilsen became a held member of the Scandinavian colony in Buenos Aires and was chairman of the Norwegian La Plata Society 1925–27.