<jats:title>Abstract</jats:title>
<jats:p>This article re-examines the vowel system of Messapic, an Indo-European language attested from the sixth to the second century <jats:sc>BCE</jats:sc> in Apulia. Given the limited corpus of inscriptions, written in a local script derived from Greek, the phonology of Messapic remains difficult to understand. Through a critical reassessment of the literature and a first-hand analysis of vowel alternations, this study offers a new chronology for some sound changes: namely, it challenges the widely accepted theory of a prehistoric across-the-board *<jats:italic>o</jats:italic> > <jats:italic>a</jats:italic> shift, drawing the possible inference that this sound change was still on-going within the historical period; in addition, in exploring the synchronic values and diachronic developments of back vowels and diphthongs, particularly within key morphological classes such as the *-<jats:italic>tor</jats:italic>‑ and *-<jats:italic>on</jats:italic>‑stems, it suggests that the monophthongization of certain diphthongs may have triggered other sound changes. This approach offers a more nuanced understanding of the evolution of Messapic vowels and attempts to unify previous phonological models.</jats:p>
