Greenback may refer to:

• A slang term used for the United States dollar.
• A modern (since 1914) United States Federal Reserve Note.
• A United States Note, (U.S. Note) among the first national United States currencies, authorized by the Legal Tender Act of 1862, and issued for more than a century, until 1971. This was the first greenback and was government-issued currency, different from the central-bank paper currency (Federal Reserve Note) that the United States began to use in 1914, and exclusively now uses. The two types of notes had similar green-inked backs, but the later Federal Reserve note was distinguised from the older U.S. Note by an green rather than red treasury seal on the obverse side of the note.

• United States Greenback Party, an American political party that was active between 1874 and 1884 which advocated government-issued currency.
• Save the Greenback, U.S. Bureau of Engraving and Printing employees, and paper and ink suppliers, opposed to phasing out the paper dollar
• Greenback, Tennessee, a city in Loudon County, Tennessee, United States
• Celestion G-12, guitar cabinet loudspeakers
• Greenback cutthroat trout, (Oncorhynchus clarki stomias), the easternmost subspecies of cutthroat trout
• an alternate name for the Bar jack, or Caranx ruber
• a surname

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