This short grammar documents the Inanwatan language, an endangered language of the Bird's Head of West Papua (Indonesia). It deals with major patterns of phonology, morphology and syntax of Inanwatan. It also contains a vocabulary, extensive texts and materials from a linguistic survey of the Inanwatan district. The introductory chapter contains a discussion of the sociolinguistic and historical context of the Inanwatan language. Special emphasis is given to the field linguistic problems that arise from describing a Papuan language in an advanced stage of generational erosion and on the basis of data in which Malay and Malayicised vernacular are often very hard to tell apart.