The slender-billed finch (Xenospingus concolor) is a species of bird in the tanager family Thraupidae.

It is restricted to southwest Peru and northern Chile, and inhabits mainly riverine vegetation along coastal valleys.

Some information has indicated that it has adapted to threats by using olive tree plantations and other artificial habitats successfully.

[2] The slender-billed finch was formally described in 1837 by the French naturalists Alcide d'Orbigny and Frédéric de Lafresnaye under the binomial name Sylvia concolor.

[3][4] The slender-billed finch is the only species placed in the genus Xenospingus that was introduced by the German ornithologist Jean Cabanis in 1867.