This chapter explores national identity as both a source of cohesion and a driver of geopolitical conflict. In an interconnected world, identity has become a tool for power, mobilization, and propaganda, shaping foreign and domestic policies. States like Russia, China, Israel, and Turkey strategically deploy narratives of national unity, historical continuity, or civilizational heritage to legitimize territorial ambitions, consolidate domestic support, and challenge perceived external threats. Russia’s “Russkiy Mir” justifies interventions in former Soviet states; China enforces assimilation in Tibet, Xinjiang, and Taiwan; Turkey evokes Ottoman heritage to expand influence; and Israel-Palestine demonstrates conflicting national narratives rooted in history and religion. Internally, rigid or exclusive national identities exacerbate social tensions, marginalizing minorities and fuelling separatist movements, civil unrest, or even ethnic cleansing, as seen in India, Catalonia, Nigeria, and Burma with the Rohingya. Conversely, inclusive national identities, emphasizing civic values over ethnicity or religion, can strengthen cohesion and democracy, exemplified by Canada’s multiculturalism, Rwanda’s post-genocide civic reconstruction, and South Africa’s “rainbow nation.” National identity also operates as a geopolitical weapon through propaganda and social media, shaping perceptions, polarizing societies, and influencing foreign policy. The chapter concludes that the future lies in constructing open, plural, and participatory national identities. Only by balancing unity with diversity can nations transform identity from a source of conflict into a foundation for cohesion, democracy, and international influence.