Spain sponsored Columbus’s first voyage through the Crown of Castile, ruled by Ferdinand II of Aragon and Isabella I of Castile.
Columbus first sought support in Portugal, but King John II did not approve his plan. He then appealed to Ferdinand and Isabella, who agreed to finance the expedition after the conquest of Granada in 1492. The voyage was organized under the authority of the Spanish monarchy, even though Columbus himself was Genoese by origin.
The expedition departed from Palos de la Frontera on August 3, 1492, with three ships: the Santa María, Pinta, and Niña. Columbus’s agreement with the monarchs promised him titles and a share of the wealth and trade generated by any territories he reached.
A common mix-up is to answer Italy because Columbus was born in Genoa, a city in present-day Italy. His birthplace and the sponsoring power were different: Genoese by birth, but sailing under the authority and financial backing of the Spanish Crown.