The Andean gull (Chroicocephalus serranus) is a species in subfamily Larinae of the family Laridae, the gulls, terns, and skimmers. It is found in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru.
The Andean gull is 42 to 48 cm long and weighs about 480 g; it is one of the larger members of its genus. The sexes are alike. Adults in breeding plumage have a glossy black hood with a white crescent behind the eye and a mostly white body with a gray back and sometimes a pink flush on the underparts. Their tail is white. The upper side of their wing is mostly gray with an alternating white-black-white-black pattern on the primaries. The underside of their wing is pale gray with a blackish outer half but for large white "mirrors" on the three outermost primaries. Their bill, legs, and feet are blackish brown with a reddish tinge and their iris is brown. Non-breeding adults have a white head and blackish legs. The Andean gull takes two years to attain adult plumage. In its first year it has some mottled black on its head, a complex black and white pattern on the wings, and a black band near the end of the tail.