The Vaux's Swift, Chaetura vauxi, breeds in highlands from southern Alaska to central California and from southern Mexico, the northern Yucatán Peninsula, to eastern Panama and northern Venezuela. The United States' populations are migratory, wintering from central Mexico south through the Central American breeding range. The resident breeding birds in the southern part of the range are sometimes considered a separate species, Dusky-backed Swift, Chaetura richmondi.

Vaux's Swift builds a cup nest of twigs and saliva on a vertical surface in a dark cavity, such as a tree hole, cliff crevice or attic. It lays three white eggs between March and July. It breeds in the mountains and foothills, mainly above 700 m, and forages over forests and more open areas, including towns.

This is a small swift, even compared to other Chaetura species, at 10.7 to 11.2 cm long and weighing 18 g. The northern populations are slightly larger at 11.5 cm. It has a a cigar-shaped body, crescentic wings and a short bluntly squared-off tail. The head, upperparts and wings are dusky black, and the underparts, rump and tail coverts are greyish brown. The throat is paler grey, becoming whitish in northern birds. The sexes are similar, but juveniles have dusky bases to the throat feathers.

This swift has more varied calls than others in the genus, with a mixture of chattering, buzzes, squeaks and chips.

This is a gregarious species, with flocks of 30 or more birds, and often with other swift species, such as White-collared, especially at weather fronts. It flies with a mixture of stiff wing-beats and unsteady glides.

Vaux's Swift feeds in flight on flying insects, including beetles, wasps, termites and flying ants.

This species was named for the American scientist William Sansom Vaux.