Azuma Old Japanese is an areal term for the two major dialects of Eastern (‘Azuma’) Japan during the eighth century: Eastern Old Japanese and Töpo-Suruga Old Japanese. This volume is an exhaustive, comparative reference grammar based on the linguistic data contained in the Man’yoshu poetic anthology (759 CE). It contains chapters dedicated to the different lexical categories, the lexicon, the phonology, and the historical development. This volume serves to fill the last remaining gap in English language scholarship on the grammar of premodern Japanese dialects, and significantly contributes to our understanding of the historical development of the earliest attested Japanese dialects. It also contains an extensive reconstruction of Proto-Japanese.