The Jago cock, also known as Gallus giganteus, is a theoretical type of poultry. It was initially documented in 1813 by Coenraad Jacob Temminck, who named it after examining a sizable foot with a 5 centimeter (2 inch) spur. Temminck speculated that it hailed from the wild in southern Sumatra and western Java. Initially, Temminck categorized large domesticated fowl under the name Gallus patavinus, derived from Padua, following Mathurin Jacques Brisson's nomenclature, as there were two Italian breeds.
Leonard Fitzinger revisited this classification in 1878. These birds were described as being sizable, with a comb extending along the eye in a straight line, thick, elevated, and appearing truncated at the top. Their throats were bare, with small wattles under the mandibles. Subsequent authors began applying the term Gallus giganteus to large domesticated fowl, including those from Malabar, as depicted in Hardwicke's collection. Temminck suggested that Gallus giganteus was among the six wild ancestors of the domestic chicken. Edward Blyth posited that domestic chickens were entirely the product of selective breeding from red junglefowl (Gallus gallus), a hypothesis also favored by Charles Darwin.