The Hartlaub's gull or king gull, (Chroicocephalus hartlaubii) is a small gull, which is a non-migratory breeding resident endemic to the Atlantic Ocean coastline of South Africa and Namibia. Although it is predominantly coastal or estuarine, it is not a pelagic species, and is rarely seen at sea far from land. It was formerly sometimes considered to be a subspecies of the silver gull (C. novaehollandiae), and, as is the case with many gulls, it has traditionally been placed in the genus Larus but is now placed in the genus Chroicocephalus.
About one half of the total population, currently estimated at about 30 000 birds, are within the Greater Cape Town area. It breeds in large colonies, and the main traditional breeding colony for the Cape Town area is on Robben Island. The adults fly to the mainland to find food for their chicks, a round trip of about 24 km.
Hartlaub's gull is 36–38 cm in length. It is a mainly white gull with a grey back and upperwings, black wingtips with conspicuous white "mirrors", and a dark red bill and legs. When breeding it has a very faint lavender grey hood, but otherwise has a plain white head. Sexes are similar. This species differs from the slightly larger grey-headed gull in its thinner, darker bill, deeper red legs, paler, plainer head, and dark eyes.