The SS Principessa Mafalda was an Italian transatlantic ocean liner built for the Navigazione Generale Italiana (NGI) company. Named after Princess Mafalda of Savoy, second daughter of King Victor Emmanuel III, the ship was completed and entered NGI's South American service between Genoa and Buenos Aires in 1909. Her sister ship SS Principessa Jolanda (1907) had sunk immediately upon launching on 22 September 1907.

On 25 October 1927, while off the coast of Brazil, a propeller shaft fractured and damaged the hull. The ship sank slowly in the presence of rescue vessels, but confusion and panic resulted in 314 fatalities out of the 1,252 passengers and crew on board the ship. The sinking resulted in the greatest loss of life in Italian shipping and the largest ever in the Southern Hemisphere in peacetime.