Greenback may refer to:
- A slang term used for the United States dollar.
- United States Note, among the first national United States currency, authorized by the Legal Tender Act of 1862. This was government-issued currency, different from the central-bank currency that the United States uses today.
- 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
