Thymallus baicalensis, also known as the Baikal black grayling, is a Siberian freshwater fish species in the salmon family Salmonidae. Thymallus baicalensis occurs in Lake Baikal, in the inflowing Selenga River and throughout the major Enisei River drainage, and also some eastern tributaries of the Ob River. The Baikal grayling can grow up to a length 38 cm and 1.2 kg weight. It mainly moves along stony bottoms at shallow depths, feeding on caddisfly and stonefly larvae, amphipod crustaceans and fish eggs.