This chapter explains how the artificial creation of the Nigerian state – spurred principally by colonialism – drove colonial and eventually Indigenous officials to promote a system of regionalism to accommodate the creation of a federal system of government. In doing so, the concept of ethnicity was arbitrarily and crudely introduced to the complex and diverse patchwork of peoples inhabiting what would become Nigeria. Regionalism fostered self-interested political groups, whereby the individual interests of Nigeria’s three principal regions (North, West, and East), each dominated by one of three major ethnic groups (Hausa/Fulani, Yoruba, and Igbo), competed amongst one another for power, leading to extraregional conflicts. Complicating this system was the presence of many hundreds of other, much smaller, minority ethnic groups. The promotion of regionalism would ultimately give rise to ethnonationalism, in which Nigeria’s three largest ethnic groups were given precedence over minority groups, leading to intra-regional conflict. The concepts of regionalism and ethnicity would become inseparably intertwined and would significantly hamper decolonization and efforts at building a consolidated and equitable state.