Historians at the Britain's University of Bristol said the Venetian-born merchant John Cabot received funding in April 1496 from the Florentine banking house Bardi in London.
Funds were provided so that Cabot could undertake expeditions "to go and find the new land," documents show.
Cabot led expeditions from Bristol during the summers of 1496 and 1497 resulting in the European discovery of North America, since the earlier voyages of Columbus had been limited to the Caribbean.
"We have long known that Italy's great merchant banks were key to the success of the ventures launched by Portugal and Spain," Bristol project leader Evan Jones said. "But it always seemed that the English ventures were an exception.
"Now it is clear that they too were part of network of Italian-financed expeditions to explore beyond the limits of the known world."
While it has long been known that Cabot received political support from Britain's king, the identity and motivations of those who financially backed the expeditions has never been known, researchers said.