The British colonial invasion of the territories that would come to constitute the nation-state of Nigeria also planted the seeds for the birth of nationalist and anticolonial movements. This chapter traces the advent and growth of Nigerian nationalism across its different phases, beginning with the immediate aftermath of the colonial invasion until the period of the 1940s. This showed how the seeds of nationalist consciousness were sown in the resistance of traditional rulers to the colonial attacks on their political authority and territorial integrity. It also showed how the alliances of these rulers with emerging Western-educated elites formed the core of the struggles against the colonial administration in the post-amalgamation period. The chapter pays attention to a variety of internal and external factors, ranging from aggressive taxation and unrepresentative government to discrimination in the civil service, Western education, and the work of Christian missionaries. It traces three kinds of formations: political organizations such as the People’s Union, the NNDP and the Nigerian Youth Movement; media outlets such as the Lagos Times and the West African Pilot; and pan-African organizations like the NCBWA.