Bachman's warbler (Vermivora bachmanii) is a possibly extinct passerine migratory bird. This warbler was a migrant, breeding in swampy blackberry and cane thickets of the Southeastern and Midwestern United States and wintering in Cuba. There are some reports of the bird from the twenty-first century, but none are widely accepted. Some authorities accept a Louisiana sighting in August 1988 as confirmed, but the last uncontroversial sightings date to the 1960s.

This bird was first recorded in 1832 by the Reverend John Bachman, who found the species near Charleston, South Carolina, and presented study skins and descriptions to his friend and collaborator, John James Audubon. Audubon never saw the bird alive but named it in honor of Bachman in 1833. An alternate common name of the species used by some 19th-century authors, paralleling similar names given to other species once placed in the genus Helinaia, is Bachman's swamp warbler.

The blue-winged and rapidly declining golden-winged warblers, also members of the genus Vermivora, are thought to be this warbler's closest relatives. There are no known subspecies.

Bachman's warbler is a sexually dimorphic species and the adults have two distinct plumages, one in the spring and one in the fall. In the spring, adult males have a yellow forehead and supercilium. The area below the bird's eye is yellow, while the lores are a dusky olive. The bird's forecrown is black with gray at the edges, while the rear crown and nape are olive-gray. The rest of the warbler's upperparts are an olive green, with the rump being the brightest. The chin and upper throat are yellow, while the center throat and upper chest are black. The belly is yellow, and the undertail coverts are white. Males in their first spring are nearly identical to the adult male, but have less black on their crown and chest.

During the spring, adult females are a light yellow in their forehead and supraloral, blending into a gray crown and nape. Its lores are a gray-olive and it has a white eye ring. The rest of the female's upperparts are an olive-green, which like the male is brightest on the rump. The chin and throat are also a light yellow, while the sides of the neck and the upper breast are gray. Older females have a few black upper breast feathers. The rest of the breast and the belly is light yellow, blending into white on the undertail coverts. The flanks are also washed with gray. First spring females resemble the adult female, but appear duller.

Bachman's warbler molts over the summer into its fall plumage. For adult males, the fall plumage is nearly identical to the spring, with the only difference being that the forecrown changes from black to gray. First year males also resemble their spring plumage, but have an olive forecrown and duller yellow underparts. Adult females possess the same plumage, although it looks fresher in the fall, while first year females have an olive-yellow forehead and a dull eyering.

Hatchlings obtain their first plumage in May and undergo their first molt in June. Juvenile Bachman's warblers have a dusky brown head and upperparts and are a paler brown below, which transitions to dull white on the lower body and undertail.

This warbler is 4.25 inches (10.8 cm) in length. It is relatively small for a warbler and has a short tail. It is unique amongst warblers for its thin and decurved bill. The Bachman's warbler's bill is blackish brown in adults and brown in the juveniles. The legs are a grayish-brown, while the eyes are dark brown.