The fork-tailed flycatcher (Tyrannus savana) is a passerine bird of the tyrant flycatcher family and is a member of a genus typically referred to as kingbirds. Named for the long, forked tail, particularly in males, fork-tailed flycatchers are seen in shrubland, savanna, lightly forested and grassland areas, from southern Mexico to Argentina. They are frequently observed on conspicuous perches whence they sally after insect prey. Northern populations near southern Mexico tend to be permanent residents, while fork-tailed flycatchers that live further south are migrants with a reputation for wandering as far north as New Brunswick, Canada.

The fork-tailed flycatcher was described in 1760 by Mathurin Jacques Brisson under the French name "le tyran à queue fourchue" (lit. 'the fork-tailed tyrant') and then again in 1780 by Georges-Louis Buffon under the name "le savana" (because it lived in savannahs), but it was not until 1802 that François Marie Daudin coined the binomial name Tyrannus savana. The type locality is Suriname.

Four subspecies are recognised:

The fork-tailed flycatcher is white below, gray above, and has a black cap. Males sometimes show a yellow crown stripe. Males also have an extremely long, forked tail, of even greater length than that of the related scissor-tailed flycatcher. Females have a somewhat shorter tail, and it is significantly shorter in juveniles.

Males are 37–41 cm (15–16 in) in length; females, 28–30 cm (11–12 in), including tail. They weigh only 28–32 g (0.99–1.13 oz), much less than closely related kingbirds, which are half the total length of this species. The tail in adult males is two to three times longer than the length of the bird from the bill to the base of the tail. Generally, males and females of the species look quite similar, but can be distinguished by the longer tail in males.

The nominate subspecies T. s. savana has a darker grey back compared to T. s. monachus and T. s. sanctaemartae, which have notable light backs that contrast greatly with their black heads. Discrete notches on the primary feathers are also quite handy in identifying subspecies.

Most fork-tailed flycatchers are migratory, but some stay year-round, especially in southern Mexico. Migratory fork-tailed flycatchers tend to have more pointed wings than nonmigratory flycatchers.

Fork-tailed flycatchers produce both vocal and nonvocal sounds. In general, they have a dry, buzzy call, and a weak "tic-note" while in flight.