The grayling (Thymallus thymallus) is a species of freshwater fish in the salmon family (family Salmonidae) of order Salmoniformes. It is the type species of its genus. Native to the Palearctic ecozone, the grayling is widespread throughout northern Europe, from the United Kingdom and France to the Ural Mountains in Russia. While it was introduced to Morocco in 1948, it does not appear to have become established there.
Arctic grayling grow to a maximum recorded length of 76 cm (30 in) and a maximum recorded weight of 3.8 kg (8.4 lb). Of typical thymalline appearance, the Arctic grayling is distinguished from the similar grayling (T. thymallus) by the absence of dorsal and anal spines and by the presence of a larger number of soft rays in these fins. There is a dark midlateral band between the pectoral and pelvic fins, and the flanks may possess a pink iridescence. T. a. arcticus has been recorded as reaching an age of 18 years.
Arctic grayling are widespread in Arctic ocean drainages from Hudson Bay, Canada to Alaska and in Arctic and Pacific drainages to central Alberta and British Columbia in Canada. They do not occur naturally in the Fraser and Columbia river basins. There are remnant native populations of fluvial Arctic grayling in the upper Missouri river drainage in the Big Hole river and Red Rock basin (“Montana Arctic grayling”). Fluvial Arctic grayling have been reestablished in the upper Ruby river, a tributary of the Beaverhead river. The native range formerly extended south into the Great Lakes basin in Michigan. They occur naturally in the Arctic ocean basin in Siberia from the Ob to Yenisei drainages and in European Russia in some tributaries of Pechora river.