Thymallus yaluensis is a putative species of freshwater fish, a grayling in the salmon family Salmonidae. It is endemic to the upper Yalu River in Korea, on the Chinese border. Thymallus yaluensis is a small fish, the maximum recorded length is 20 cm (8 in). "It has the most beautiful form and fins of a freshwater fish" in Korea. 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.