Krimchak, a Jewish dialect of the Crimean Tatar language attested since the 13th century, is in danger of disappearing. The Krimchak Dictionary is the first attempt to present the lexicon of this dialect with translations into both English and Russian. It contains a total of about 5,000 Krimchak words and loan words as well as set expressions appearing in both religious and secular sources. The derivations contained in this dictionary are based on Etimologicheskij slovar tjurkskix jazykov by E. Sevortjan, on the Dictionnaire Armeno-Kyptchak by E. Tryjarski, as well as on the Codex Cumanicus by K. Gronbech. The work presents the pre-modern stage of Krimchak in comparison with various modern Turkic languages and dialects, including Turkish, Nogay, Karaim, Tatar and Mishar, etc. It is based on the wide scope of Krimchak writings, including sections of the Hebrew Bible, the history of 20th-century Krimea, teaching texts for children, prose and poetry, and it also synthesizes vocabulary from Krimchak sources written in Hebrew, Russian and Latin letters. For loan words, the foreign source languages are given, and all words and illustrative examples from the written Krimchak sources are provided with a transcription based on the Latin alphabet. The dictionary has both a scientific and a practical purpose. It is meant for specialists in Turkic philology and for specialists in Jewish dialects and Biblical studies, and for specialists of Russian and Ukrainian history. At the same time, it can also be used as a reference book by Krimchak readers seeking to enlarge their active vocabulary.