There are several competing explanations for the rise in ethnic nationalisms in Nigeria, but there is an agreement that identity politics and conflicts tend to incubate and thrive best in underdeveloped settings. To this can be added the crises produced by prolonged military rule, during which the intensity of contestations for power translated the quest for ethnic ascendancy into the rule rather than the exception. This essay provides the contexts and extenuating circumstances in which ethnic nationalisms by the Yoruba and the Ijaw in southern Nigeria became salient and militant from the 1990s onward. Despite concrete variations in their ethno-nationalist projects, the Yoruba and the Ijaw are shown to be similar in several respects: both, for instance, contain salient strands of 'self-determination' translating at best to pseudo-separatist inclinations towards the decentralization and devolution of power and authority as constituted presently in Nigeria.