Tundra and Kolyma Yukaghir are highly endangered languages spoken in the extreme North-East of Siberia and usually considered unrelated to other language families. This dictionary is the first relatively complete source of information on the Yukaghir lexicon. It presents in comparative format all known lexemes from all known varieties of Yukaghir, both modern and extinct. Based on this material it provides a reconstruction of the common ancestor of the different varieties of Yukaghir, which has not previously been attempted. The dictionary also suggests etymologies for many Yukaghir words and includes possible cognates from other languages, mainly Uralic and Altaic.