The Australian aboriginal language Kuuku Ya'u and its closely related dialect Umpila are described. An introductory chapter provides information on the classification of the languages, linguistic type, and dialect groups. The second chapter outlines aspects of the phonology of Kuuku Y'au and Umpila, including phonemes, vowel length, consonant length, word stress, and phonotactics. Chapter 3, on morphology, describes the parts of speech and details the morphology of nouns, pronouns, and verbs. The fourth chapter describes the syntax of simple sentences; noun phrases; complex sentences; mood and aspect; and sentence interjections, particles, and clitics. A brief chapter, chapter 5, is devoted to metaphorical extensions of body part terms. Chapter six contains five texts with morphological analysis and English translation. Chapter seven is a guide to the pronunciation of letters and phonemes. The final chapter consists of a two-way glossary. The English-to-Kuuku Ya'u/Umpila word list is organized by semantic category, and the Kuuku Ya'u/Umpila-to-English list is organized alphabetically. A brief list of references and a map are appended. (MSE)