The thick-billed kingbird (Tyrannus crassirostris) is a large bird in the family Tyrannidae, the tyrant flycatchers.
Adults are dusky olive-brown on the upperparts with light underparts; they have a long dark brown or black tail. The underside is a dull white to pale yellow. They have a yellow patch on their crown, but is not visible very often. The bill on this species, for which it is named, is rather large and stocky compared to other members of this group and it is one of this kingbird's most distinguishing characteristics. The call is a loud, whistled pwaareeet.