A copy of the first map to portray the world as a globe is set to raise up to £800,000 at auction.
Christie's, in London, is due to sell the 1507 drawing - the first to label the New World as "America" - in June.
It is one of four surviving copies of the map, made by German cartographer Martin Waldseemuller.
It followed claims by Italian explorer Amerigo Vespucci that the New World was a separate continent - not part of Asia, as Christopher Columbus had said.
The name "America" was derived from Vespucci's first name, and the map was the first to distinguish North and South America and to show the Pacific Ocean.
The copy being auctioned lay undiscovered in the stock of a European collector until two years ago.
He only realised the value of his possession after seeing a newspaper article about another Waldseemuller map.
Tom Lamb, director of Christie's book and manuscript department in London, described the find as "truly groundbreaking".
"This is one of the most exciting discoveries of my career, and represents the pinnacle in the history of map-making," he said.
Although Christopher Columbus landed in America before Vespucci, he was convinced the land mass was Asia.
It was Vespucci, after sailing there a few years later, who put forward the then-revolutionary argument that it was an entirely new continent.
In 1505 Rene II, the Duke of Lorraine, gathered a group of scholars at the Monastery of Saint Die des Vosges near Strasbourg, led by Waldseemuller, to create a new map of the world.
They worked from a French translation of Vespucci's voyages and, in 1507, published a work called "Cosmographiae Introductio" arguing the existence of a new land mass to the west.
They followed it within a month with the map showing the continent for the first time and clearly marking it "America".
"This simple sheet of paper holds so many new and anticipated discoveries, all created with an enormous leap of faith by a venerable geographer in a small town in Lorraine," Mr Lamb said.
The map is set to be auctioned as part of a sale of important maps, atlases and globes on 8 June.