Seigniorage /ˈseɪnjərɪdʒ/, also spelled seignorage or seigneurage (from Old French seigneuriage 'right of the lord (seigneur) to mint money'), is the increase in the value of money due to money creation minus the cost of producing the additional money. Monetary seigniorage is where government bonds are exchanged for newly created money by a central bank, allowing debt monetization ("borrowing" without repaying).

Seignorage can also refer to:

Seigniorage is the positive return, or carry, on issued notes and coins (money in circulation). Demurrage, the opposite, is the cost of holding currency.

An example of an exchange of gold for "paper" where no seigniorage occurs is when a person has one ounce of gold, trades it for a government-issued gold certificate (providing for redemption in one ounce of gold), keeps that certificate for a year, and redeems it in gold. That person began with and ends up with exactly one ounce of gold.

In another scenario, instead of issuing gold certificates a government converts gold into non-gold standard based currency at the market rate by printing paper notes. A person exchanges one ounce of gold for its value in that currency, keeps the currency for one year, and exchanges it for an amount of gold at the new market value. If the value of the currency relative to gold has changed in the interim, the second exchange will yield less (or more) than one ounce of gold (assuming that the value, or purchasing power, of one ounce of gold remains constant through the year). If the value of the currency relative to gold has decreased, the person receives less than one ounce of gold and seigniorage occurred. If the value of the currency relative to gold has increased, the person receives more than one ounce of gold and demurrage occurred; seigniorage did not occur.

The 50 State Quarters series of quarters (25-cent coins) began in 1999. The U.S. government thought that many people, collecting each new quarter as it rolled out of the United States Mint, would remove the coins from circulation. Each complete set of quarters (the 50 states, the five inhabited U.S. territories, and the District of Columbia) is worth $14.00. Since it costs the mint about five cents to produce one quarter, the government made a profit when someone collected a coin. The Treasury Department estimates that it earned about $6.3 billion in seigniorage from the quarters during the program.

Some countries' national mints report the amount of seigniorage provided to their governments; the Royal Canadian Mint reported that in 2006 it generated $93 million in seigniorage for the government of Canada. The U.S. government, the largest beneficiary of seigniorage, earned about $25 billion in 2000. For coins only, the U.S. Treasury received 45 cents per dollar issued in seigniorage for the 2011 fiscal year.

Occasionally, central banks have issued limited quantities of higher-value banknotes in unusual denominations for collecting; the denomination will usually coincide with an anniversary of national significance. The potential seigniorage from such printings has been limited, since the unusual denomination makes the notes more difficult to circulate and only a relatively-small number of people collect higher-value notes.