Working within a broad theoretical and disciplinary framework this dissertation explores a range of programmes of cultural and religious enterprise in which Medici women in the late sixteenth to early seventeenth centuries were engaged. I seek to examine the ways in which patronage activities and the wider entrepreneurial, aesthetic and devotional acts of the Florentine grand duchesses of this period worked to position them culturally, spiritually, politically and dynastically. Drawing on existing scholarship in the fields of art and architectural patronage, public festivals and rituals, pilgrimage and collecting practice, I offer new analyses based on empirical research and documentary evidence, which retrieve and assess aspects of the cultural activities of Giovanna of Austria, wife of Francesco de' Medici, grand duke of Tuscany; Cristina of Lorraine, wife of Francesco's successor, Ferdinando I; and Maria Maddalena of Austria, wife of Cosimo II. Where appropriate, these activities are read in relation to those of Maria de' Medici, their relative and queen of France. The project opens with the arrival in Florence in 1565 of Giovanna of Austria, an event celebrated as a triumphal entry. Developing themes of display, spectacle and women's representation in public space, I move on to consider the roles of the later grand duchesses by tracing the activities which made them visible, and exploring how the rituals in which they participated fashioned and projected their identities as brides, mothers, grand duchesses and, eventually, regentesses. I examine the grand duchesses' pilgrimages to Loreto, identifying these as spectacular processional rituals with special spiritual and political resonances. I consider the concealed spaces of female Medicean devotion: the convents which they visited, supported and adapted to their own needs, and Maria Maddalena of Austria's private chapel in Palazzo Pitti in which she preserved a vast collection of valuable relics and reliquaries. Questions on devotional and secular activities, on public and private space, on propagandistic display and religious observance, that link the diverse studies of this dissertation, are addressed in the final chapter in relation to Maria Maddalena's lavish programme of rebuilding and decoration at the suburban palace she bought in the 1620s, the Villa del Poggio Imperiale. This project seeks broadly to draw out, delineate and contextualise the limits and possibilities of Medici women's cultural activities in the period to bring more clearly into focus their social, political and gendered dimensions.