This study aims to present a vision of pluralism and the crisis of nation-building in Mauritania, by looking at the roots and consequences of the crisis. This study falls in the context of the well-known regional studies field in some literature, and it assumes that the reality of pluralism has affected the Mauritanian state in two problems, the problem of political identity: is it an Arab or African country? And the problem of social identity: is the state of Negroes or the Arabs? Thus, you see that pluralism is responsible for the crisis of state building, given the specificity of this pluralism. It also contributes to the continued domination of military rulings, as it weakens society and kills its living forces by neutralizing its goals from the public sphere to what is personal and private. Indeed, the reality has proven that even if it defends domestic issues but it is backed by external powers and this increases the risk of deviation On the right thing. The study concludes that the tribal society is also less dangerous than the ethnic community, due to the danger that the tribal society may cause from the danger that it will doubtless have on the future of the state.

Key words: pluralism, ethnic pluralism, tribe, tribalism, crisis, country