This research seeks to acquire a deep understanding of how spirituality and mission correlate and shape each other. An initial review of missiological texts has revealed that spirituality is not often (nor explicitly) taken into consideration by missiologists. Likewise, mission generally does not occupy a central place within the academic discipline of spirituality. I contend that spirituality is the motor of mission and missiology and therefore cannot be only briefly mentioned or omitted from missiological discourse. This thesis explores this relationship with a specific focus on the Comboni Missionary Sisters. It explores the mission spirituality of their founder, Daniel Comboni, how this is taken up by the Comboni Missionary Sisters and how it shapes their lives and their being in mission. The research also aims to foster some transformations. It explores new ways for the Sisters to express their ways of being in mission in the context(s) in which they live, in order to be faithful to Comboni’s charism as well as to be a relevant presence today. The thesis proposes that mission spirituality be studied and lived by making use a Mission spirituality spiral. Its six dimensions are: spirituality, at the centre and all along the spiral; encounter with other(s) and with the context; context analysis; theological reflection (encounter with Scripture and Tradition); discernment for transformative ways of being in mission and reflexivity. A qualitative analysis is presented from interviews conducted with fifteen Comboni Missionary Sisters working in various continents. Genuine encounter with the Triune God, with the other(s), with the context and its analysis, and encounter with Scripture and Tradition lead to transformation in the person and subsequently to finding new ways of being in mission. The mission spirituality spiral is used as an analytical tool to study the mission spirituality of Comboni and the Comboni Missionary Sisters and also as a mobilising tool. Suggestions for further areas of research are made. The thesis concludes with some personal learning and transformation. / Christian Spirituality, Church History and Missiology / D. Th. (Missiology)