Cassin's kingbird (Tyrannus vociferans) is a large tyrant flycatcher native to western North America.

Cassin's kingbird was formally described in 1826 by English naturalist William Swainson under the current binomial name Tyrannus vociferans.

[4] Two subspecies are recognised:[5] Adults have a gray head with slightly darker cheeks; a dark unforked tail with a buffy fringe and gray-olive underparts.

The Cassin's kingbird primarily feeds on insects it preys upon from high perches by hawking.

Like many other flycatchers, Cassin’s kingbirds will often pump their tail up and down while perched in order to deter predators.