Arnold IV of Loon (Looz) (died between November 1272 and October 1273; most likely on February 22, 1273), was Count of Loon from 1227 to 1273 and Count of Chiny (as Arnold II) from 1228 to 1268. He was the son of Gérard III, Count of Rieneck and Cunegonde von Zimmern.
In 1244, a war is contrasted with Henry of Heinsberg. The dispute between the pope and the emperor festered, the pope excommunicated the emperor, and called on voters to choose another: William of Holland and Arnold attended his coronation. To keep their fiefdoms from suffering the disorders of anarchy following the death of Frederick II, Bishop of Liege, the Duke of Brabant, and Count of Gelderland entered a confederation entrusted with their common defense.
Arnold enjoyed the esteem and confidence of his contemporaries, and arbitrated several disputes to this title. He granted freedom to Hasselt and Kuringen, granted city status in Bilzen and made several donations to monasteries.