The Old Ethiopian language (Gz) has been attested in inscriptions since the early centuries AD. After the Christianization of Ethiopia, it became the liturgical language of the Ethiopian Orthodox Church and maintained its predominant role as a medium of written communication until the 19th century. During this time, numerous works of ecclesiastical and secular literature were produced: Bible translations, hagiography, theology, liturgy, royal chronicles, and magical literature. Many of these texts are translations from Greek (in late antiquity) or from Arabic (in the Middle Ages and early modern period); alongside these, there are also many original Ethiopian creations. Even today, Gz is taught and learned in the ecclesiastical institutions of Ethiopia and Eritrea. Stefan Weninger's grammar presents the Old Ethiopian script, phonology, morphology, and syntax in detail and based on sources. The presentation is primarily synchronic, but where possible and meaningful, the language use of different historical periods and source groups is highlighted. In this respect, it also has the character of a historical grammar. The citations and examples are presented in the Ethiopian original script, with accompanying transcriptions to facilitate usage. In citations from translation literature, reference is often made to the source text, which provides a firmer basis for evaluating the citations. Three indices (linguistic keywords, Ethiopian words and morphemes, cited individuals) and 36 paradigm tables complement the grammar.