Killis (كلّيس), a town of southern Turkey in the vilayet of Aleppo, 60 m. north of the city of Aleppo. It is situated in an extremely fertile plain, and is surrounded with olive groves, the produce of which is reckoned the finest oil of all Syria; and its position on the carriage-road from Aleppo to Aintab and Birejik gives it importance. The population (20,000 in 1911) consisted largely of Circassians, Turkomans and Arabs, the town lying just on the northern rim of the Arab territory.