This dissertation offers an in-depth investigation of the phonology of Munduruku, a Tupi language spoken in the Amazonian basin of Brazil, approached from three interrelated perspectives: phonetic, phonological and diachronic. It examines (i) the Munduruku vowel and consonant inventories, (ii) syllable structure and syllabification, (iii) phonotactic patterns, (iv) nasal harmony, (v) consonant mutation, (vi) tone system and the tone-creaky voice interaction, (vii) reduplication, and (viii) the phonological behavior of various affixes. The phonetic investigation focuses on several acoustic properties of segments (i.e. vowels and consonants), and on phonological contrasts observed in vowels, in particular the oral-nasal and modal-creaky voice oppositions, in addition to tonal distinctions. This is done with a view to determining how and to what extent such phonetic realizations can be imposed on phonological representations. These issues constitute an important part of the study, and are particularly relevant to the discussion about the coarticulatory effects observed in the realization of stops, nasals and laryngeals. The study also offers a formal account of all major phonological processes attested in the language such as syllabification, nasal harmony, consonant mutation, tone, etc. The theoretical model adopted here is Optimality Theory (OT), which defends a representation of the structural design of grammars based upon a ranking of universal constraints. Each chapter contributes to the development of an OT-based grammar of the phonology of Munduruku by examining new aspects of the language, and by situating them in a large-scale scenario until the OT-grammar is assembled. This result is presented in the last chapter. In search of evidence for the synchronic analysis, and for a better understanding of some uncharacteristic patterns, the study turns to the historical development of the language. Using data from Kuruaya, a sister language to Munduruku, hypotheses about the stage that preceded both languages, Proto-Munduruku, are made available. In recovering this stage, and the stage that preceded the modern period, it is possible to recover many of the changes the grammar has undergone and which culminated in the synchronic patterns. Ultimately, this study argues for an approach to synchronic grammars as a composite of universal and language-specific properties, determined by diachronic changes. / Arts, Faculty of / Linguistics, Department of / Graduate