Thymallus yaluensis, also known as Yalu grayling, is a putative species of freshwater ray-finned fish in the genus Thymallus (graylings) of the family Salmonidae. It is endemic to the upper Yalu River on the China-North Korea border.^[1]

Thymallus yaluensis is a small fish, with a maximum recorded length of 20 cm (7.9 in).^[1] It is renowned in Korea for having "the most beautiful form and fins of a freshwater fish".^[1]

Some confusion exists regarding the identity of T. yaluensis, as it closely resembles the Arctic grayling (Thymallus arcticus) in form and has often been treated as a subspecies (T. a. yaluensis).^[2] However, FishBase recognizes it as an independent species.^[1] According to mitochondrial DNA, T. yaluensis is, however, inseparable from the Amur grayling (Thymallus grubii), and was suggested to be a junior synonym of that.^[3] Confusingly, it has also been reported from widely separate regions including Siberia, the Alps in Europe, and the northern Mississippi River drainage in North America.^{[citation needed]}