The purpose of the article is to analyze and characterize the Roman military diploma as a historical document. The research methodology consists in the use of general scientific methods and principles: a comparative and historiographical analysis, systematization of scientific literature, research works and documents; the principle of historicism, systematicity, scientificity and objectivity. The scientific novelty: on the basis of a wide range of the research es for the first time in the Ukrainian historiography the significance of the Roman military diploma as a historical document ha s been characterized; the prospects of the study of diplomata militum as the sources for the study of the Roman influences on the territory of ancient Ukraine have been elucidated . The Conclusions . During m any years the research es in the field of epigraph ics , including the study of military diplomas, became an important component in the reconstruction of the personnel of the Roman auxiliary units – auxilia, the names of these units, and helped reproduce some other aspects of functioning related not only to the military history. This refers to the administrative apparatus of the Empire, in particular, in addition to the then ruling emperor, in the diplomas the names of consuls, the governor of the province and the commanders of these military units are recorded ; you can also trace the stages of their career – cursus honorum. Analyzing these documents, we can determine the status and place of retired servicemen in their residence places after the honorary resignation ( honesta missio ), to trace the stages and nature of the Romanization of the provinces owing to the quantity of diplomas found and the information about the retiree’s family. It ha s been also noted that the Roman military diplomas from the territory of Ukraine can be an important source for studying some aspects of the history of ancient Ukraine. Nowadays, many issues related to the Roman military diplomas remain not analyzed. For instance, the place of publishing of the imperial constitutions (tabula aenae (aerae)), from which the diplomas were copied , has not yet been identified. The place the diplomas were stored has not been identified either. It is unknown why bronze documents were stopped issuing in the ІІІd century and what are the reasons for their appearance on the territory of the Ukrainian lands. Despite all these gaps, many aspects of this issue have already been studied and this gives us the opportunity to look in a new way at the functioning of such a complex part of the Roman state mechanism as the Roman army.