This dissertation interrogates the discursive and material developments of Republican ideology in the context of colonial conquest, decolonial movements, and settler nuclear imperialism, from the Third Republic (1870) until today. Indeed, the prevalence of Republican universalism in France has shaped a potent and default race blind position that often prevents any cohesive national reckoning with colonialism and slavery. Since the early 2000s, however, the rise of French postcolonial studies has allowed for this memory to re- emerge, particularly in the context of the Caribbean, Algeria, and West Africa. Yet, the question of race and its entwinement with Republican universalism as well as colonial expansion remain minimally studied, particularly in regions such as Oceania. In the age of climate change, then, the historical entanglements of settler colonialism, modernity, and environmental racism requires greater foregrounding. Drawing from Postcolonial and Decolonial theory, Critical Race Studies, Indigenous Studies, and Environmental Humanities, I explore the modes of production, erasure, and remembrance of colonialism and racialization across the French continuum through Republican universalism on the one hand, and atomic modernity on the other. From political actors such as Jules Ferry, Charles de Gaulle, and Emmanuel Macron; postcolonial thinkers such as Frantz Fanon, Édouard Glissant, and Homi Bhabha; Indigenous theorists such as Glenn Coulthard, Eve Tuck, and Jodi Byrd; and Mā’ohi writers Chantal Spitz and Titaua Peu, I contend that race and settler nuclear colonialism ambivalently figure in French Republican laws, policies, and discourses, and how racialized and colonized subjects across the Francophone world are resisting this haunting structure, particularly in the nuclearized Oceanian region.