Current ethnic conflict in Ethiopia is not a simple byproduct of Multinational federalism and politicization of ethnicity since 1991. Regardless of the contradictions and debates over the core causes of ethnic conflict in Ethiopia, it is impossible to fully comprehend it without a thorough and honest examination of the pre-1991 country's history in terms of ethnicity and ethnic conflict. The article analyzed the historical root causes of ethnic conflict in Ethiopia by taking Minilik’s II and HaileSelassie’s I regimes into account. Hence, a Dialectical approach and historical method were employed to conduct a critical investigation of the core causes of ethnic conflict. The article found that the country's current ethnic politics and ethnic warfare sowed during the imperial regime. Minilik II and his successor conquered, confiscated, subjugated, enslaved, and dehumanized the southern nations, nationalities, and people in the consecration of Ethiopia's current territory. During imperial administrations, Ethiopia was seen as a prison-house of people. Ethnic identity has been taboo during the imperial regimes of Ethiopia. The article found that the imperial regimes of Ethiopia were the precursor to both immediate and potential ethnic-based detestation, animosity, and violence that resulted in the country's lengthy and deadly civil wars. Based on a dialectical method, this article discovered that the process of Ethiopian state creation resulted in sustainable and predictable cyclical rotation of contradiction and contestation between thesis and antithesis, without creating strong syntheses. Moreover, the misappropriation of concepts of nationalism and nation-building has been common in the country's political history