Yuan dynasty banknotes were the earliest fiat money.

Fiat money is money that derives its value from government regulation or law. The term fiat currency is used when the fiat money is used as the main currency of the country. The term derives from the Latin fiat ("let it be done", "it shall be").^[1]

Fiat money originated in 11th century China,^[2] and its use became widespread during theYuan and Ming dynasties.^[3] During the 13th century, Marco Polo described the fiat money of the Yuan Dynasty in his book The Travels of Marco Polo.^[4][5] The Nixon Shock of 1971 ended the direct convertibility of the United States dollar to gold. Since then all reserve currencies have been fiat currencies, including the U.S. dollar and the Euro.^[6]