The lesser koa finch (Rhodacanthis flaviceps) is an extinct species of Hawaiian honeycreeper in the subfamily Carduelinae of the family Fringillidae.

[1] The only specimens of the lesser koa finch ever caught were a family group with members of different ages and sex, ideal for study.

The females were almost indistinguishable from the species' larger relative, the greater koa finch (Rhodacanthis palmeri), other than the fact that the former were slightly darker in color.

[citation needed] The extinction of this species and other koa finches seems to have been caused by habitat destruction, and not by climatic variation nor mosquito-vectored diseases.

On the island of Hawaiʻi, koa finches persisted until the late 19th century, when their upland refugium was degraded by logging, ranching, and intensified predation by the black rat.