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.

In 1910, she played a part in developing long-distance radio communication when Guglielmo Marconi conducted experiments on board.

[3] Specifically designed for voyages between Genoa and Buenos Aires, Principessa Mafalda was considered the best ship on this route for several years, travelling at a relatively rapid 18 knots.

[6] On 11 October 1927 Principessa Mafalda sailed from Genoa for Buenos Aires with intermediate stops scheduled at Barcelona, Dakar, Rio de Janeiro, Santos, and Montevideo.

Principessa Mafalda left Barcelona almost a day late due to mechanical problems, and several times, she slowed to a complete stop on the high seas, sometimes for hours.

At the stop at Cape Verde, Captain Gulì telegraphed the company to request a replacement vessel but was told, "Continue to Rio and await instructions."

[9] Around 17:15 hours on 25 October 1927, near the Abrolhos Archipelago, 130 kilometres (80 mi) off Salvador de Bahia, Brazil, the ship was rocked by several strong shudders.

[8] However, on the bridge, the engineer reported that the starboard propeller shaft had indeed fractured, but it had also traveled off its axis and cut a series of gashes in the hull.

[12] Captain Gulì directed the launching of the lifeboats from the bridge with his megaphone; the evacuation was orderly at first, but panic began to quickly spread when power failed at 22:03, plunging the vessel into darkness.

Passengers started jumping into the sea, where sharks attacked some, and Gulì, realizing that the ship was now sinking fast, ordered all the remaining lifeboats to be lowered; the considerable list to port hampered the launching of the starboard lifeboats, several of which were damaged against the hull and rendered unusable.

[13] Captain Gulì went down with the ship, and the chief engineer, Silvio Scarabicchi, reportedly committed suicide by shooting himself.

[14][15] Gulì was posthumously decorated for bravery at sea, as were the two radio operators, Luigi Reschia and Francesco Boldracchi, who had remained at their post until they drowned.

Reports of gunfire, sharks in the water, exploding boilers, and nearby ships refusing to assist were widely published but never confirmed.