Oneida is an endangered Iroquoian language spoken fluently by fewer than 250 people. This is a comprehensive dictionary of the Oneida language as used in Ontario, where most of the surviving speakers reside. The dictionary contains both Oneida-English and English-Oneida sections. The Oneida-English portion includes some 6000 entries, presenting lexical bases, particles and grammatical morphemes. Each entry for a base shows several forms; illustrates inflection, meaning and use; and gives details regarding pronunciation and cultural significance. The English-Oneida entries direct the reader to the relevant base in the Oneida-English section, where technical information is provided. Completing the volume is a set of appendices that organizes Oneida words into thematic chategories.