The black-capped vireo (Vireo atricapilla) is a small bird native to the United States and Mexico. It was listed as an endangered species in the United States in 1987. Successful conservation efforts on the U.S. Army's Fort Hood and Fort Sill led to delisting the black-capped vireo in 2018. The IUCN lists the species as vulnerable.
The black-capped vireo is a songbird about 12 cm (4.5 inches ) in length. Sexually mature males are olive green above and white below with faint yellow flanks. The crown and upper half of the head is black with a partial white eye ring and lores. The iris is brownish-red and the bill is black. Females are duller in color than males and have a slate-gray crown and underparts washed with greenish yellow. First-year males often have more extensive gray in the cap, similar to adult females.