The Nao was a Spanish-Portuguese ship of the Middle Ages and early Age of Exploration.
A forerunner carried crusaders to the Holy Land in the 13th century, and under various names (nef, nave, nau, nao, all of which are variants of the Latin navis: ship), and through various developments, became the generic sail-powered large (for its time) trading vessel suitable for work in both the Mediterranean and Atlantic. There is a 13th century city seal (Winchester) showing a nef whilst a Catalan model of a nao exists that tells us much about the vessel in that place at that time. It is thought that by the 15th century it was almost indistinguishable from the carrack.
Columbus referred to the Santa Maria as a nao, although it may have been a larger caravel than its two mates. Whatever, a century later both the nao and the caravel had all but disappeared, having being found unsuitable for the rigours of the trans-Atlantic trade. Its place was taken by the galleon.