The thick-billed euphonia (Euphonia laniirostris) is a species of bird in the family Fringillidae, formerly placed in the Thraupidae. This euphonia measures 10 cm (3.9 in). The male has entirely yellow underparts from throat to vent save for a small terminal patch of white on the undertail. Upperparts are a dark blue-black except for the yellow crown patch which extends from the bill over the head to just past the eye. The female, like many euphonias, is dull olive above and yellow below.