The Chestnut-backed Antbird, Myrmeciza exsul, is a passerine bird in the antbird family. It is a resident breeder in tropical Central and South America from eastern Nicaragua to western Ecuador. It occurs in lowlands up to 900 m altitude.
This is a common bird in the understory thickets of wet forest, especially at edges, along streams and in old treefall clearings, and in adjacent tall second growth. The female lays two purple or red-brown spotted white eggs, which are incubated by both sexes, in an untidy cup nest which is constructed from vines, plant fibre and dead leaves and placed low in vegetation. The male and female parents both feed the chicks.
The Chestnut-backed Antbird is heavy-bodied and short-tailed, typically 14 cm long, and weighing 28 g. Both sexes have a pale blue bare patch of skin around each eye. The adult male has a blackish head, neck and breast, and the rest of the upperparts, wings and tail are chestnut. The flanks and the lower belly are a somewhat darker brown. The female has a brownish-black head and neck, but this does not extend to the breast. Her underparts are a darker chestnut in Caribbean birds, but more rufous in the Pacific lowlands. Young birds are duller and slatier than the adults.
This species has a grating naar call, and the male's song is a whistled peeet peeew answered by the female's higher pitched version.
The Chestnut-backed Antbird is normally found as pairs throughout the year, but occasionally joins mixed-species feeding flocks or army ants. It feeds on insects, other arthropods, and sometimes small frogs or lizards taken from leaf litter and vine tangles in low vegetation or on the ground. It is easier to hear than see in its dense habitat, but can be attracted by imitating its whistled song. It may then give a territorail display with puffed-up body, drooped wings, and pumping tail.