This study focuses on the Jesuit mission in Ethiopia (1557-1632). It presents a comprehensive history of the mission, from its inception during the reign of the Portuguese King Dom Manuel I, through its phase of expansion up to the expulsion of the Jesuit missionaries. Being the first mission personally conceived by the founder of the Society of Jesus, Ignatius of Loyola, the Ethiopian was also the last of the 'imperial' undertakings of the Society to fall, after the collapse of the projects in Japan and Mughal India in the 1610s and 1620s, respectively. The Ethiopian enterprise unfolded in lands far beyond Spanish or Portuguese control and under the protection of a powerful regional monarchy, the Ethiopian Solomonic House. The mission, which had a modest beginning during the last decades of the sixteenth century, turned in the next century to be an ambitious project of transformation of Ethiopian church and society. The Jesuits made use of a persuasive approach, their intellectual supremacy and links to sophisticated cultures - Renaissance and Manneristic Europe and Mughal India - to win over Ethiopian nobility, high clergy and state officials. In this study I focus on the mission taking into consideration both the geopolitical and the religious-cultural aspects. The thesis is aimed as being an institutional history of the mission; I distinguish its main actors and focus in its different stages of development. In addition, I also take into account factors hitherto disregarded in historical literature, such as the role played by local and regional intermediaries and the indigenous agency of missionary discourse. Prosopography and quantitative methods have been used to shed light on to all the men that were involved in this project and also to get acquainted with the different social groups the missionaries interacted with in India and in Ethiopia. The thesis also benefits from a large compilation of images which illustrate the importance that the arts played in the project to ‘reduce’ Ethiopian Christianity. The study aims to be a further contribution to the growing interest this mission has attracted from scholars. Although this has recently been the object of intense scrutiny, there were still many neglected episodes. The thesis critically reviews some traditional assumptions found in historical literature and offers new ways of understanding specific aspects of the mission.