Benedykt Dybowski (1833–1930) – one of the most important European zoologists of the second half of the 19th and the first decades of the 20th c. – was a man extraordinarily active both in science and society. Perceived primarily as a pioneer of Darwinism in Poland, he achieved his greatest professional success through his study of the ichthyofauna of Lake Baikal and the East Siberian rivers Angara, Yenisei, and Selenga. This work examines the Siberian period of Dybowski’s life in the context of his faunistic research on the world’s deepest lake.