On January 23, 1961, a group of Portuguese and Spanish opposition movement members seized control of the Santa Maria, a 609-foot-long (186 m), 20,900-ton Portuguese luxury cruise liner. Also known as Operation Dulcinea, the code name given it by its chief architect and "leader" Henrique Galvão, it was a rebel terrorist operation against the Government of Portugal. The action has also been referred to as "piracy", although it does not fit the international definition of piracy involving an attack of one vessel on another for private ends.
Owned by the Lisbon-based Companhia Colonial de Navegação, the ship was the second largest ship in the Portuguese merchant navy at the time and along with her sister ship, the was among the most luxurious Portuguese-flag liners of that time.
The ship was primarily used for colonial trade to the Portuguese overseas provinces of Angola and Mozambique, in Africa, and migrant transportation to Brazil. The ship's mid-Atlantic service was also viewed as rather out of the ordinary: Lisbon to Madeira, to Tenerife, to La Guaira, to Curaçao, to Havana (later San Juan), and lastly Port Everglades. The average trade for this gray-hulled ship was mostly migrants toVenezuela and the general passenger traffic.