Xantus's Hummingbird, Hylocharis xantusii, is a medium-sized hummingbird. It is 8-9 cm long, and weighs approximately 3-4 g.

Adults are colored predominantly green on their upperparts and back. The tail is darkly colored and straight. The most prominent feature is the white eyestripe found in both males and females. The stripe is further enhanced by a black eyestripe below the white one. Both have cinnamon brown underparts, with the brown extending further up the throat in the female. Green replaces the brown in the throat of the male. The bill of the male is straight and very slender. It is red in coloration, and shows a black tip. His crown and face is bluish-black.

The breeding habitat occurs in various habitats of southern Baja Peninsula of Mexico where it is considered endemic. It has been recorded as a vagrant up the Pacific coast of North America to British Columbia in Canada.

These birds feed on nectar from flowers and flowering trees using a long extendable tongue or catch insects on the wing.

This hummingbird was named after John Xantus de Vesey (Xantus János), a Hungarian zoologist.