The Warbling Vireo, Vireo gilvus, is a small songbird.

Adults are 12 cm long and weigh 12 g. They are mainly olive-grey on the head and upperparts with white underparts; they have brown eyes and the front of the face is light. There is a white supercilium. They have thick blue-grey legs and a stout bill. Western birds are generally smaller.

Their song is a cheerful warble, similar to that of the Painted Bunting. There are subtle differences in song between eastern and western birds. Some authorities split the eastern and western races of this species into separate species:

Western Warbling Vireo, V. swainsonii

Eastern Warbling Vireo, V. gilvus The Brown-capped Vireo (Vireo leucophrys), a resident species in Central America and northern South America, is sometimes considered to be conspecific with Warbling Vireo.

The Warbling Vireo's breeding habitat is open deciduous and mixed woods across most of North America, from Alaska to Mexico.

These birds migrate to Mexico and Central America.

They forage for insects in trees, hopping along branches and sometimes hovering. They also eat berries, especially before migration and in winter quarters, where they are - like other vireos - apparently quite fond of Gumbo-limbo (Bursera simaruba) seeds, though they will not venture into human-modified habitat to get them.

They make a deep cup nest suspended from a tree branch or shrub, placed relatively high in the east and lower in the west. The male helps with incubation and may sing from the nest.