The greater koa finch (Rhodacanthis palmeri) was a species of finch in the family Fringillidae. It was found only in the Hawaiian Islands. It has been extinct since the late 19th century. The last confirmed sighting was in 1896, although there were sporadic later reports. Like its close relative the lesser koa finch, this bird lived in small stretches of mesic forest on the Big Island of Hawaiʻi. These forests were dominated by its preferred food source, koa (Acacia koa), and were logged and replaced with pasture beginning in 1850. Grazing by cattle inhibited the regeneration of koa forest, while introduced black rats (Rattus rattus) preyed on young birds. Avian pox (Poxvirus avium) and malaria (Plasmodium relictum), spread by mosquitoes, may have also been a factor. However, even before these issues became important, the koa finches were probably already living in marginal habitat due to the loss of lowland koa forest, as evidenced by the extinction of the other koa finch species (which lived on lower-elevation islands) prior to European contact.