Greenback may refer to:

Currency

* Greenback (1860s money), a fiat currency issued during the American Civil War *Greenback, a nickname used for the United States dollar in the financial press in other countries, or slang for the US paper dollar * Greenback Party, an American political party active between 1874 and 1884 which advocated non-gold-backed government currency

Fish

* Greenback cutthroat trout (''Oncorhynchus clarki stomias''), the easternmost subspecies of cutthroat trout * Greenback flounder (''Rhombosolea tapirina'') * Greenback horse mackerel (''Trachurus declivis''), a species of jack * Greenback stingaree (''Urolophus viridis'') * An alternate name for the Bar jack (''Caranx ruber'')

Other uses

* Greenback, Tennessee, United States, a city * "Greenbacks", a 1955 song by Ray Charles * Celestion G-12, guitar cabinet loudspeakers * Baron Silas Greenback, a fictional villainous toad in ''Danger Mouse'' (TV series) * "Greenbacks" (''Once Upon a Time''), an episode of the seventh season of ''Once Upon a Time'' {{disambig ja:紙幣#その他