As the custodian of the planet's largest tropical rainforest and a pivotal voice from the Global South, Brazil's trajectory through three decades of global climate governance presents a profound and instructive narrative. This chapter examines Brazil's journey from a sovereignty-conscious observer to a period of constructive leadership, through a phase of stark regression, and into its current potential for renewed global engagement. It argues that the nation's climate diplomacy has been fundamentally shaped by the persistent tension between its domestic development imperatives and its escalating global environmental responsibilities. By tracing this evolving role, the chapter illuminates the complex interplay of geopolitics, economic ambition, and ecological urgency that defines not only Brazil's past but also critically informs its future path and, by extension, the prospects for global climate stability.