This book is a part of a two-volume reference grammar of Tundra Yukaghir, a critically endangered language spoken in the north-eastern part of Siberia. The grammar is the first substantial English-language description of the language, which aims to address the linguistic phenomena presently regarded as crucial in any grammatical account as comprehensively as possible. It introduces a large variety of data and will be inherently valuable as a piece of language documentation. Although illustrative examples from previous literature are cited, most examples come from newly collected data reflecting the modern state of the language. The grammar of Tundra Yukaghir has played relatively little role in the considerations of modern linguists, as there are numerous aspects which have not received systematic treatment previously or have not been addressed at all. For a language as little researched as Tundra Yukaghir, any such aspect may turn out to be of potential linguistic significance. Thus, this detailed, systematically organized and conventionally represented grammatical description will prove useful for linguists working on broader issues. It will provide a reference source for both native speakers and researchers in linguistics, whether descriptively, typologically or theoretically inclined.