The survival and success of religious reform groups in the late medieval period was often due to the efforts of an ecclesiastical patron, a powerful and often wealthy individual who exerted their influence on behalf of the group or their leaders and spokesmen. This thesis uses the wealth of documentation available on the Spiritual Franciscans to explore the origin, development and wider effect of the relationships between the most powerful ecclesiastical patrons of the reformers and their clients, spokesmen for the Italian Spirituals at the papal court who were taken into the patrons’ households for years or even decades. During that time, the political fortunes of the different groups of Spiritual Franciscans fluctuated dramatically: in only a handful of years they went from hopeful expectation at the Council of Vienne c. 1311 to heresy trials, imprisoned spokesmen and friars burned at the stake c.1317-1318. Using testaments from the patrons’ families and the patrons themselves, the thesis explores the possible reasons for the patrons’ initial attraction to their Spiritual Franciscan clients. Letters, chronicles and exegetical texts written by the clients during and after their time in the patrons’ households are examined along with papal registers and other narrative and epistolary sources to develop models of the nature and progression of the patronage relationship, and how it survived in the face of periods of intense disapproval and harassment from the papacy, other prelates and some members of the Franciscan hierarchy. After establishing a framework for the progression of the patronage relationship, evidence of art patronage and other religious and patronage interests that the patrons and clients shared is used to develop a deeper understanding of how the patrons’ choice to involve themselves with the Spiritual Franciscans positively or negatively affected others in their orbit, especially their other clients.