The Albacora class is diesel-electric attack submarine (SSK) developed for the Portuguese Navy based on the French Daphné class submarine. In 1964, the Portuguese government ordered the construction of four of this class at the Dubigeòn-Normándie Shipyard to create the 4th submarine flotilla. With the first submarine commissioned on October 1, 1967, the Portuguese Navy started to have a submarine able to operate in both coastal and oceanic zones, especially in the Portuguese exclusive economic zone.