This monograph is a grammatical description of Tondano, an endangered and under-documented Austronesian (AN) language spoken in the northern part of the island of Sulawesi, Indonesia. It is a modified version of the related doctoral dissertation completed at La Trobe University, Bundoora, Victoria, Australia (2015). The chapters herein begin by outlining relevant socio-historical information relating to the Tondano speech community, before providing detailed explanations of the sound system (phonetics and phonology), word structure (morphology), and phrase and sentence structure (syntax) of the language. This description seeks to be as complete as possible, while at the same time acknowledging any descriptive shortcomings, either due to a lack of data, a lack of analytical clarity, or simply due to considerations of space. The data used for this grammar come from extensive in situ fieldwork (2011–2015). In essence, the analysis takes a theory-neutral approach. While it does not utilise a specific theoretical framework, parts of the terminology, methodology, and analysis conform to those of Basic Linguistic Theory. There is a strong emphasis on using data which are as naturalistic as possible, and which has been collected, collated, and analysed in collaboration with native speakers in the Tondano speech community. For all levels of linguistic structure under description, language examples taken from primarily spontaneous communicative events are provided. In terms of issues relating to Austronesian typology, and aspects of broader cross-linguistic typology, these are mentioned where deemed necessary but are not the primary focus of this work. The principal audience for this book is scholars and students of languages and linguistics, along with anyone with an interest in the anthropology and linguistics of the Austronesian cultures of Maritime Southeast Asia.