Valkó County (Hungarian: Valkó vármegye, Croatian: Vukovska županija, Serbian: Вуковска жупанија) was an administrative unit (county) of the medieval Kingdom of Hungary.[1] It was established in the 13th century, and included most territories of the present day Vukovar-Syrmia County, in modern Croatia, and western parts of the present day Syrmia District, in modern Serbia. The most important cities of the county were Vukovar and Ilok. Its territory was conquered by the Ottoman Turks in the first half of the 16th century.[2]