This thesis determines the impact of Catholic activism in south-west France during the 1560s. Using manuscript and archival material, it examines the nascence, infrastructure and aims of the various ligues and associations of the period, and assesses their ability to secure hegemony by usurping local administrative and military apparatus. The thesis is divided into four parts: Part I studies Catholic activism at Bordeaux and the Bordelais. Chapters 1 and 2 establish the demography and structure of government there and evaluate antecedents to the ligues of the 1560s: namely the activities of the confraternity of Saint- Yves, the basoche and the syndicat of 1561. Chapter 3 examines the role of the Catholic nobility in the internecine struggles of the period, and Chapter 4 explores the post-1568 domination of military and bureaucratic offices at Bordeaux by a coalition of leading Catholic activists. Part II focuses on events at Agen and the Agenais. Chapter 5 details the establishment of an executive council of Catholic notables within the town, while Chapter 6 assesses the role of the local nobility in supporting this coalition government after 1563. Part III concentrates on affairs at Toulouse. Chapter 7 examines the birth of formal Catholic activism within the town, focussing on the enterprises of the confraternity, basochiens and militant court officials. Chapter 8 analyses the reinvigoration of Catholic endeavours at Toulouse after 1567, gauging the success of a policy to finance the Catholic war effort by sequestering Protestant goods, and appraising the somewhat anachronistic phenomenon of the croisade of 1568. Part IV considers the extent to which national and European dimensions influenced the form and nature of Catholic activism during the 1560s. Chapter 9 examines the impact of Catholic grandee patronage on the ligues of the south-west, and assesses the resurgence in confraternal activism after 1567. Chapter 10 examines the influence of Spain and the papacy on the evolution of the associations, and explores the level of reciprocity between ligueurs and European potentates. Chapter 11 details the ambitions of Catholic powers to remove the Calvinist queen of Navarre, Jeanne d' Albret, from power in Béarn and Navarre, and assesses the role played by the ligueurs in this enterprise.